Arithmetic operators in Rust - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Rust code using arithmetic operators?

Consider the following Rust code snippet. What will it print when run?

Rust

fn main() {
    let a = 10;
    let b = 3;
    let result = a % b + a / b * b;
    println!("{}", result);
}

A 10

B 3

C 9

D 1

💡 Hint

Remember the order of operations: division and multiplication happen before addition.

The expression is evaluated as (a % b) + ((a / b) * b). Here, a % b is 10 % 3 = 1, a / b is 10 / 3 = 3 (integer division), so 3 * 3 = 9. Adding 1 + 9 gives 10.

❓ Predict Output

intermediate

What is the value of x after this Rust code runs?

Look at this Rust code. What is the final value of x?

Rust

fn main() {
    let mut x = 5;
    x += 3 * 2 - 4 / 2;
    println!("{}", x);
}

A 8

B 11

C 9

D 10

💡 Hint

Calculate the expression on the right side first, then add to x.

The expression is 3 * 2 - 4 / 2 = 6 - 2 = 4. Then x += 4 means x = 5 + 4 = 9.

❓ Predict Output

advanced

What does this Rust code print?

Analyze this Rust code snippet and determine its output.

Rust

fn main() {
    let a = 7;
    let b = 2;
    let c = a / b;
    let d = a as f64 / b as f64;
    println!("{} {}", c, d);
}

A 3 3.5

B 3 3

C 3.5 3

D 3.5 3.5

💡 Hint

Integer division truncates, but casting to float allows decimal division.

a / b is integer division: 7 / 2 = 3. Casting to f64 makes it floating point division: 7.0 / 2.0 = 3.5.

❓ Predict Output

advanced

What is the output of this Rust code with mixed arithmetic?

What will this Rust program print?

Rust

fn main() {
    let x = 4;
    let y = 3;
    let z = (x + y) * (x - y) / y;
    println!("{}", z);
}

A 7

B 2

C 1

D 3

💡 Hint

Calculate inside parentheses first, then multiply, then divide.

(4 + 3) = 7, (4 - 3) = 1, so 7 * 1 = 7, then 7 / 3 = 2 (integer division).

❓ Predict Output

expert

What is the output of this Rust code involving overflow with wrapping arithmetic?

Consider this Rust code using wrapping_add. What will it print?

Rust

fn main() {
    let max = u8::MAX; // 255
    let result = max.wrapping_add(10);
    println!("{}", result);
}

A 0

B 265

C 10

D 9

💡 Hint

Wrapping addition wraps around on overflow instead of panicking.

u8 max is 255. Adding 10 wraps around: 255 + 10 = 265 mod 256 = 9.

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