Arithmetic operators in Rust - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the '+' operator do in Rust?

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

beginner

How do you perform multiplication in Rust?

Use the '*' operator to multiply two numbers. For example, 4 * 5 equals 20.

intermediate

What is the result of 10 / 3 in Rust when using integer types?

When dividing integers, Rust performs integer division, so 10 / 3 equals 3 (the decimal part is dropped).

beginner

What does the '%' operator do in Rust?

The '%' operator gives the remainder of a division. For example, 10 % 3 equals 1.

intermediate

Can you use arithmetic operators with floating-point numbers in Rust?

Yes, you can use '+', '-', '*', and '/' with floating-point numbers (like f32 or f64). The operations work as expected with decimals. The '%' operator is not supported for floating-point types in Rust.

What is the result of 7 + 5 in Rust?

A 75

B 2

C 12

D Error

The '+' operator adds numbers, so 7 + 5 equals 12.

Which operator gives the remainder of a division?

A %

B -

C +

D /

The '%' operator returns the remainder after division.

What happens when you divide two integers in Rust and the result is not whole?

A It rounds up

B It rounds down

C It returns a float

D It drops the decimal part

Integer division drops the decimal part, so 10 / 3 equals 3.

Which operator is used for multiplication in Rust?

A /

B *

C +

D -

The '*' operator multiplies two numbers.

Can you use the '+' operator with floating-point numbers in Rust?

A Yes

B No

C Only with integers

D Only with strings

The '+' operator works with floating-point numbers as well as integers.

Explain how the '%' operator works in Rust and give an example.

Think about what is left after dividing one number by another.

Describe what happens when you divide two integers in Rust and the result is not a whole number.

Rust does not round but cuts off the decimal.

Practice

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

easy

A. The - operator

B. The / operator

C. The * operator

D. The % operator

Solution

1. Step 1: Understand the meaning of each operator

   The / operator divides, * multiplies, - subtracts, and % gives the remainder after division.

2. Step 2: Identify the operator for remainder

   The % operator returns the remainder when one number is divided by another.

3. Final Answer:

   The % operator -> Option D

4. Quick Check:

   Remainder operator = % [OK]

Hint: Remainder always uses % in math [OK]

Common Mistakes:

• Confusing / with %, thinking / gives remainder
• Using * or - for remainder
• Mixing up operator symbols

2. Which of the following is the correct way to write multiplication of two variables a and b in Rust?

easy

A. a * b

B. a x b

C. a . b

D. a & b

Solution

1. Step 1: Recall Rust arithmetic syntax

   Rust uses * for multiplication, not x, ., or &.

2. Step 2: Confirm correct operator

   The expression a * b correctly multiplies a and b.

3. Final Answer:

   a * b -> Option A

4. Quick Check:

   Multiplication operator = * [OK]

Hint: Use * for multiplication in Rust [OK]

Common Mistakes:

• Using x instead of *
• Using . or & which are not arithmetic
• Confusing syntax with other languages

3. What is the output of the following Rust code?

let x = 10;
let y = 3;
let result = x / y;
println!("{}", result);

medium

A. 4

B. 3.3333

C. 3

D. Syntax error

Solution

1. Step 1: Understand integer division in Rust

   Both x and y are integers, so x / y performs integer division, dropping decimals.

2. Step 2: Calculate integer division

   10 divided by 3 is 3.3333, but integer division truncates to 3.

3. Final Answer:

   3 -> Option C

4. Quick Check:

   Integer division truncates decimals = 3 [OK]

Hint: Integer division drops decimals, use floats for precise result [OK]

Common Mistakes:

• Expecting decimal result with integer division
• Confusing integer and float division
• Assuming syntax error due to println!

4. Identify the error in this Rust code snippet:

let a = 5;
let b = 2;
let c = a / b.0;
println!("{}", c);

medium

A. Variables a and b are not declared

B. Using .0 on integer causes error

C. Missing semicolon after println!

D. Division operator / is invalid

Solution

1. Step 1: Analyze the expression a / b.0

   The code tries to access .0 on b, which is an integer, not a tuple or struct.

2. Step 2: Understand why .0 causes error

   Only tuples or structs have fields like .0; integers do not, so this causes a compile error.

3. Final Answer:

   Using .0 on integer causes error -> Option B

4. Quick Check:

   Integer has no .0 field = error [OK]

Hint: Only tuples/structs have .0, not integers [OK]

Common Mistakes:

• Thinking / is invalid operator
• Missing semicolon causes error
• Assuming variables are undeclared

5. You want to calculate the average of two integers a and b in Rust and get a float result. Which code snippet correctly does this?

hard

A. let avg = (a + b) as f64 / 2.0;

B. let avg = (a + b) / 2.0;

C. let avg = (a + b) / 2;

D. let avg = (a + b) / 2 as f64;

Solution

1. Step 1: Understand type conversion for float division

   To get a float result, convert integers to float before division.

2. Step 2: Check each option for correct syntax and types

   let avg = (a + b) / 2; does integer division, no float result. let avg = (a + b) as f64 / 2.0; converts sum to f64, divides by 2.0 (float), correct. let avg = (a + b) / 2.0; divides integer sum by float 2.0 without conversion, invalid. let avg = (a + b) / 2 as f64; tries to cast 2 to f64 before division (due to `as` precedence), invalid.

3. Final Answer:

   let avg = (a + b) as f64 / 2.0; -> Option A

4. Quick Check:

   Convert to float before dividing by float [OK]

Hint: Cast sum to float before dividing by float [OK]

Common Mistakes:

• Dividing integers by float without cast
• Casting after division
• Using integer division expecting float result