Arithmetic operators in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the + operator do in Python?

The + operator adds two numbers together. For example, 3 + 2 equals 5.

beginner

What is the result of 7 - 4 in Python?

The result is 3 because the - operator subtracts the right number from the left number.

beginner

Explain the * operator in Python.

The * operator multiplies two numbers. For example, 5 * 6 equals 30.

beginner

What does the / operator do?

The / operator divides the left number by the right number and gives a decimal result. For example, 8 / 4 equals 2.0.

intermediate

What is the difference between / and // operators?

The / operator gives a decimal (float) result, while the // operator gives the whole number part only (floor division). For example, 7 / 2 is 3.5, but 7 // 2 is 3.

What is the result of 4 + 5 * 2 in Python?

A 14

B 18

C 13

D 10

Multiplication happens before addition, so 5 * 2 = 10, then 4 + 10 = 14.

Which operator gives the remainder of a division?

A +

B %

C //

D /

The % operator gives the remainder after division.

What does 10 // 3 return?

A 3

B 3.33

C 1

D 4

// does floor division, so it returns the whole number part only.

What is the output of 2 ** 3?

A 9

B 6

C 8

D 5

** is the power operator, so 2 to the power of 3 is 8.

Which operator would you use to multiply two numbers?

A +

B /

C -

D *

The * operator multiplies two numbers.

List the basic arithmetic operators in Python and explain what each one does.

Think about adding, subtracting, multiplying, dividing, and powers.

Explain the difference between / and // operators with examples.

One gives decimals, the other gives whole numbers.

Practice

1. Which arithmetic operator in Python is used to find the remainder of a division?

easy

A. **

B. //

C. %

D. +

Solution

1. Step 1: Understand the meaning of each operator

   The operator % gives the remainder after division, // gives the floor division result, ** is for power, and + is for addition.

2. Step 2: Identify the operator for remainder

   The remainder operator is %, which returns the leftover part after dividing two numbers.

3. Final Answer:

   % -> Option C

4. Quick Check:

   Remainder operator = % [OK]

Hint: Remainder operator looks like a percent sign % [OK]

Common Mistakes:

• Confusing // (floor division) with %
• Using ** instead of %
• Thinking + gives remainder

2. Which of the following is the correct operator syntax to calculate 5 to the power of 3 in Python?

easy

A. 5 ^ 3

B. pow(5, 3)

C. 5 ^^ 3

D. 5 ** 3

Solution

1. Step 1: Recall Python's power operator syntax

   Python uses ** to calculate powers, so 5 ** 3 means 5 to the power of 3.

2. Step 2: Check other options for correctness

   5 ^ 3 is bitwise XOR, 5 ^^ 3 is invalid syntax, and pow(5, 3) is a function call but not an operator syntax.

3. Final Answer:

   5 ** 3 -> Option D

4. Quick Check:

   Power operator = ** [OK]

Hint: Use ** for power, not ^ or ^^ [OK]

Common Mistakes:

• Using ^ instead of ** for power
• Trying ^^ which is invalid
• Confusing function pow() with operator syntax

3. What is the output of the following code?

result = 17 // 4
print(result)

medium

A. 4.25

B. 4

C. 1

D. Error

Solution

1. Step 1: Understand floor division operator //

   The operator // divides and returns the largest whole number less than or equal to the result.

2. Step 2: Calculate 17 // 4

   17 divided by 4 is 4.25, floor division drops the decimal part, so result is 4.

3. Final Answer:

   4 -> Option B

4. Quick Check:

   17 // 4 = 4 [OK]

Hint: Floor division drops decimals, so 17//4 is 4 [OK]

Common Mistakes:

• Confusing // with / which gives float
• Expecting 4.25 instead of 4
• Thinking // rounds up

4. Find the error in this code snippet:

num = 10
result = num % 0
print(result)

medium

A. ZeroDivisionError at runtime

B. No error, output is 0

C. SyntaxError due to % operator

D. TypeError because 0 is int

Solution

1. Step 1: Understand modulo operator with zero

   The modulo operator % cannot divide by zero; it causes an error.

2. Step 2: Identify the error type

   Dividing or modulo by zero raises a ZeroDivisionError at runtime.

3. Final Answer:

   ZeroDivisionError at runtime -> Option A

4. Quick Check:

   Modulo by zero causes ZeroDivisionError [OK]

Hint: Modulo by zero causes runtime error, never allowed [OK]

Common Mistakes:

• Thinking it causes syntax error
• Expecting output 0 instead of error
• Confusing with TypeError

5. You want to calculate the area of a square with side length stored in variable side. Which expression correctly uses arithmetic operators to do this?

hard

A. area = side ** 2

B. area = side // 2

C. area = side + side

D. area = side * 2

Solution

1. Step 1: Recall formula for square area

   The area of a square is side length multiplied by itself, or side squared.

2. Step 2: Match formula with operators

   Using side ** 2 calculates side to the power of 2, which is correct for area.

3. Final Answer:

   area = side ** 2 -> Option A

4. Quick Check:

   Square area = side squared = side ** 2 [OK]

Hint: Square area = side squared, use ** 2 [OK]

Common Mistakes:

• Using side * 2 which doubles side, not area
• Using side + side which adds sides, not area
• Using floor division // which is incorrect