Python, Concept by Concept › Numbers & Arithmetic

Exercises: Numbers & Arithmetic

Core: Exercises 1–11 are the main path. More Practice: Exercises 12–18 give extra reps. Challenges: Exercises 19–23 are optional stretch work; no core exercise depends on them.

For every exercise, follow the specification and produce the exact output shown. Run your cell and compare every capital letter, space, punctuation mark, and number with the worked sample. Write the lines directly.

Exercise 1: Supply Total

An art table has several packs with the same number of pencils in each pack. It needs the total number of pencils.

Specification: Given packs and pencils_per_pack, multiply them and print exactly Total pencils: <total>.

Worked sample — given values:

packs = 6
pencils_per_pack = 8

Expected output:

Total pencils: 48

Real program

The real program reads the pack count and pencils per pack with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: one line

Your code

packs = 6
pencils_per_pack = 8

# Calculate and print the exact total.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

multiply them

For parents and teachers: report a problem

Exercise 2: Trip Time

A trip schedule stores one duration in minutes but displays complete hours and leftover minutes.

Specification: Given the non-negative integer total_minutes, use // and % to print exactly <hours> hours <minutes> minutes.

Worked sample — given values:

total_minutes = 185

Expected output:

3 hours 5 minutes

Real program

The real program reads the trip length in minutes with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: one line

Your code

total_minutes = 185

# Split the time and print the exact schedule line.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

use // and %

For parents and teachers: report a problem

Exercise 3: Equal Share

Four teammates share a given number of meters of ribbon equally. The result should use regular division.

Specification: Given ribbon_meters and teammates, use / to print exactly Meters each: <share>. Show Python's exact float output.

Worked sample — given values:

ribbon_meters = 14
teammates = 4

Expected output:

Meters each: 3.5

Real program

The real program reads the ribbon length and number of teammates with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: one line

Your code

ribbon_meters = 14
teammates = 4

# Divide and print the exact float output.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

use / to print exactly

For parents and teachers: report a problem

Exercise 4: Next-Year Age

A saved age arrived as text. It must become a number before Python can add one.

Specification: Given age_text, convert it with int(), add 1, and print exactly Next year: <age>.

Worked sample — given values:

age_text = "12"

Expected output:

Next year: 13

Real program

The real program reads the age as text with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: one line

Your code

age_text = "12"

# Convert the quoted digits, calculate, and print.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

convert it with int()

For parents and teachers: report a problem

Exercise 5: Compare Two Scores

A practice board needs direct True or False answers to two questions: whether the first score is higher, and whether it is at least as high.

Specification: Given first_score and second_score, first compare them with > and print the boolean result directly. Then compare them with >= and print that boolean result directly.

Worked sample — given values:

first_score = 18
second_score = 15

Expected output:

True
True

Real program

The real program reads the two scores with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: several lines

Your code

first_score = 18
second_score = 15

# Print both comparison results directly.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

compare them with > and print the boolean result directly
Then compare them with >= and print that boolean result directly.

For parents and teachers: report a problem

Exercise 6: Two-Digit Report

A display separates the tens and ones places of a two-digit number.

Specification: Given number, which is an integer from 10 through 99, use // and % to print Tens: <tens> and Ones: <ones> on separate lines.

Worked sample — given values:

number = 73

Expected output:

Tens: 7
Ones: 3

Real program

The real program reads the two-digit number with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: several lines

Your code

number = 73

# Split the two-digit number and print both labels.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

use // and %

For parents and teachers: report a problem

Exercise 7: Repair the Age Label

An age label stops with a TypeError because it tries to join text and an integer with +.

Specification: Repair the broken instruction by converting age with str() so it prints exactly Age: 12. Put the repaired instruction in an empty cell in your exercises notebook.

Worked sample — broken instruction:

age = 12
print("Age: " + age)

Expected output after the repair:

Age: 12

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: one line

Your code

age = 12
print("Age: " + age)

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

converting age with str()

For parents and teachers: report a problem

Exercise 8: Price Calculator

A shop needs the cost of two items at the same price. The given price is saved as text, as it would be when read from input.

Specification: Given price_text, convert it with float(), multiply the number by 2, and print exactly Two cost: <total>.

Worked sample — given values:

price_text = "3.5"

Expected output:

Two cost: 7.0

Real program

The real program reads the price with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: one line

Your code

price_text = "3.5"

# Convert the fixed text, calculate, and print.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

convert it with float()

For parents and teachers: report a problem

Exercise 9: Coin Change

A coin counter trades cents for the fewest quarters, then dimes, nickels, and pennies.

Specification: Given non-negative cents, use // and % to print Quarters: <count>, Dimes: <count>, Nickels: <count>, and Pennies: <count> on separate lines. Add a purpose comment explaining the coin calculation.

Worked sample — given values:

cents = 83

Expected output:

Quarters: 3
Dimes: 0
Nickels: 1
Pennies: 3

Real program

The real program reads the amount of cents with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: several lines

Your code

cents = 83
# Explain the purpose of your coin calculation.
# Calculate and print each coin count.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

use // and %
Add a purpose comment explaining the coin calculation.

For parents and teachers: report a problem

Exercise 10: Seconds Breakdown

A timer stores a duration in seconds and needs a readable breakdown.

Specification: Given non-negative seconds, use // and % to print complete hours, remaining minutes, and remaining seconds on three labeled lines. Add a purpose comment explaining the breakdown.

Worked sample — given values:

seconds = 4000

Expected output:

Hours: 1
Minutes: 6
Seconds: 40

Real program

The real program reads the duration in seconds with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: several lines

Your code

seconds = 4000
# Explain the purpose of your time breakdown.
# Calculate and print the three labeled parts.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

use // and %
Add a purpose comment explaining the breakdown.

For parents and teachers: report a problem

Exercise 11: Boolean Report

A scoreboard needs three direct yes-or-no checks for one score.

Specification: Given score, print the boolean results of score >= 60, score == 100, and score != 0, in that order, one per line.

Worked sample — given values:

score = 66

Expected output:

True
False
True

Real program

The real program reads the score with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: several lines

Your code

score = 66
# Print the three boolean results directly.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

print the boolean results of score >= 60, score == 100, and score != 0

For parents and teachers: report a problem

Exercise 12: More Practice: Three-Digit Sum

A place-value puzzle adds the three digits of a number.

Specification: Given a three-digit integer number, separate its digits with // and %, then print their sum.

Worked sample — given values:

number = 468

Expected output:

Real program

The real program reads the three-digit number with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: a number

Your code

number = 468
# Split the digits and print their sum.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

separate its digits with // and %

For parents and teachers: report a problem

Exercise 13: More Practice: Power Pair

A square and a cube both grow from the same side length.

Specification: Given side, use ** to print Square: <value> and Cube: <value> on separate lines.

Worked sample — given values:

side = 7

Expected output:

Square: 49
Cube: 343

Real program

The real program reads the side length with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: several lines

Your code

side = 7
# Calculate and print the square and cube.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

use **

For parents and teachers: report a problem

Exercise 14: More Practice: Clock Arithmetic

A twelve-hour clock wraps around after 12 rather than showing hour 0.

Specification: Given an hour from 1 through 12 and non-negative added hours, calculate (hour - 1 + added) % 12 + 1 and print <result> o'clock.

Worked sample — given values:

hour = 10
added = 5

Expected output:

3 o'clock

Real program

The real program reads the starting hour and added hours with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: one line

Your code

hour = 10
added = 5
# Use the given wraparound formula and print the new hour.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

calculate (hour - 1 + added) % 12 + 1

For parents and teachers: report a problem

Exercise 15: More Practice: Progress Bar

A ten-slot progress bar fills one slot per ten points.

Specification: Given a score from 0 through 100, calculate filled = score // 10, then build and print "#" * filled + "-" * (10 - filled).

Worked sample — given values:

score = 38

Expected output:

###-------

Real program

The real program reads the score with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: one line

Your code

score = 38
# Build the ten-slot bar and print it.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

calculate filled = score // 10
then build and print "#" * filled + "-" * (10 - filled)

For parents and teachers: report a problem

Exercise 16: More Practice: Box Banner

A lab sign frames a fixed-width title.

Specification: Given title = "STAR LAB" (8 characters), build the three-line picture using "-" * 10 for the top and bottom. Save each row in a named string variable and print the exact rows.

Worked sample — given values:

title = "STAR LAB"

Expected output:

+----------+
| STAR LAB |
+----------+

Real program

The real program reads an 8-character title with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: several lines

Your code

title = "STAR LAB"
# Build each row as a named string and print the picture.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

using "-" * 10 for the top and bottom
Save each row in a named string variable

For parents and teachers: report a problem

Exercise 17: More Practice: Precedence Predictions

An expression can change its value when operators group differently.

Specification: Without running the expressions first, predict the values of 6 + 4 * 2, (6 + 4) * 2, 20 // 3 % 4, 2 ** 3 * 2, and 7 + 1 > 2 * 4, in that order. Write the five predictions as comments, then check them with Python.

Worked sample — given values:

6 + 4 * 2
(6 + 4) * 2
20 // 3 % 4
2 ** 3 * 2
7 + 1 > 2 * 4

Expected output:

14
20
2
16
False

How this is checked: You check this one yourself, against the list below.

Your code

# Prediction 1:
# Prediction 2:
# Prediction 3:
# Prediction 4:
# Prediction 5:
# Then check each expression with Python.

The site cannot check this one. Run your program, then tick each item below when your work does it.

Check your work

Without running the expressions first, predict the values
Write the five predictions as comments, then check them with Python.

For parents and teachers: report a problem

Exercise 18: More Practice: Read the ValueError

A conversion crashes when decimal text is passed to int().

Specification: Read the broken int("6.25") instruction, then repair it with float() and print the resulting number. Put the repaired instruction in the starter cell.

Worked sample — given values:

print(int("6.25"))

Expected output:

6.25

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: a number

Your code

# Replace the broken conversion with float() and print its value.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

repair it with float()

For parents and teachers: report a problem

Exercise 19: Reverse Two Digits

Challenge

A number puzzle reverses the two places of a given two-digit number.

Specification: Given number, which is an integer from 10 through 99, separate its tens and ones digits. Build the reversed integer with arithmetic and print exactly Reversed: <number>.

Worked sample — given values:

number = 42

Expected output:

Reversed: 24

Real program

The real program reads the two-digit number with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: one line

Your code

number = 42

# Split, rebuild in reverse order, and print.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

separate its tens and ones digits
Build the reversed integer with arithmetic

For parents and teachers: report a problem

Exercise 20: Three-Digit Places

Challenge

A place-value display separates every digit of a three-digit number.

Specification: Given number, which is an integer from 100 through 999, use arithmetic with non-negative operands to print Hundreds: <digit>, Tens: <digit>, and Ones: <digit> on separate lines.

Worked sample — given values:

number = 582

Expected output:

Hundreds: 5
Tens: 8
Ones: 2

Real program

The real program reads the three-digit number with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: several lines

Your code

number = 582

# Separate and print all three digits.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

use arithmetic with non-negative operands

For parents and teachers: report a problem

Exercise 21: The 1089 Trick

Challenge

A three-digit number can hide a surprising constant.

Specification: Given a three-digit number whose hundreds digit is greater than its ones digit, reverse its digits as a three-digit place-value calculation. Because the hundreds digit is larger than the ones digit, the original number is the larger one — subtract the reversed number from it. Reverse the difference as three digits using // 100, // 10 % 10, and % 10; then print the sum of the difference and its reverse. A difference of 99 must be treated as 099, whose reverse is 990.

Worked sample — given values:

number = 841

Expected output:

Real program

The real program reads the three-digit number with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: a number

Your code

number = 841
# Reverse, subtract, reverse the three-digit difference, then print the sum.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

reverse its digits as a three-digit place-value calculation
subtract the reversed number from it
Reverse the difference as three digits using // 100, // 10 % 10, and % 10

For parents and teachers: report a problem

Exercise 22: Receipt Line

Challenge

A receipt adds two prices and always shows cents.

Specification: Given first_price and second_price, add them and print Total: $<amount> with exactly two digits after the decimal point using :.2f.

Worked sample — given values:

first_price = 2.4
second_price = 3.15

Expected output:

Total: $5.55

Real program

The real program reads the two prices with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: one line

Your code

first_price = 2.4
second_price = 3.15
# Add the two prices and print the formatted total.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

using :.2f

For parents and teachers: report a problem

Exercise 23: Framed Title

Challenge

A team poster surrounds a known-width title with stars.

Specification: Given title = "GO TEAM" (7 characters) and width = 11, build a top and bottom row of "*" * width and a middle row * GO TEAM *. Save each row in a named string variable and print the exact three-line picture.

Worked sample — given values:

title = "GO TEAM"
width = 11

Expected output:

***********
* GO TEAM *
***********

Real program

The real program reads a title and a width four larger than the title's length with input().

How this is checked: Checked by comparing what your program prints with the expected output.

Answer format: several lines

Your code

title = "GO TEAM"
width = 11
# Build each row as a named string and print the picture.

Also check yourself

The automatic check cannot see these, so tick each one when your work does it.

build a top and bottom row of "*" * width
Save each row in a named string variable

For parents and teachers: report a problem

Back to Numbers & Arithmetic