Arithmetic operators in Javascript - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of mixed arithmetic operations

What is the output of the following JavaScript code?

Javascript

const result = 10 + 5 * 2 - 8 / 4;
console.log(result);

A 16

B 24

C 18

D 20

💡 Hint

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

Multiplication and division are done first: 5 * 2 = 10, 8 / 4 = 2. Then addition and subtraction: 10 + 10 - 2 = 18.

❓ Predict Output

intermediate

Result of increment and decrement operators

What will be logged to the console after running this code?

Javascript

let x = 5;
console.log(x++ + ++x);

A 12

B 11

C 10

D 13

💡 Hint

Remember that x++ uses the value before increment, ++x increments before use.

x++ returns 5 then x becomes 6; ++x increments x to 7 then returns 7; sum is 5 + 7 = 12.

❓ Predict Output

advanced

Output with modulus and exponentiation

What is the output of this code snippet?

Javascript

const a = 7 % 3;
const b = 2 ** 3;
console.log(a + b);

A 9

B 11

C 10

D 8

💡 Hint

Calculate modulus and exponentiation separately, then add.

7 % 3 is 1 (remainder), 2 ** 3 is 8, sum is 1 + 8 = 9.

❓ Predict Output

advanced

Division and floating point precision

What will this code output?

Javascript

console.log(0.1 + 0.2 === 0.3);

A TypeError

B false

C true

D undefined

💡 Hint

Think about how computers handle decimal numbers.

Due to floating point precision, 0.1 + 0.2 is not exactly 0.3, so the comparison is false.

🧠 Conceptual

expert

Understanding operator precedence and associativity

Consider the expression: 4 + 3 * 2 ** 2 / 4 - 1. What is the final value?

A 8

B 7

C 9

D 6

💡 Hint

Remember the order: exponentiation, multiplication/division, addition/subtraction, and left-to-right associativity for same precedence.

2 ** 2 = 4; then 3 * 4 = 12; 12 / 4 = 3; then 4 + 3 = 7; finally 7 - 1 = 6.

Practice

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

easy

A. %

B. /

C. **

D. *

Solution

1. Step 1: Understand the remainder operator

   The operator % returns the remainder after division of two numbers.

2. Step 2: Compare with other operators

   / is division, ** is power, and * is multiplication, so they don't give remainder.

3. Final Answer:

   % -> Option A

4. Quick Check:

   Remainder operator = % [OK]

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

Common Mistakes:

• Confusing division / with remainder %
• Using * or ** instead of %
• Thinking + or - can give remainder

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

easy

A. 5 ** 3

B. 5 ^^ 3

C. 5 ^ 3

D. pow(5, 3)

Solution

1. Step 1: Identify the power operator in JavaScript

   JavaScript uses ** to calculate powers, like 5 ** 3 means 5 to the power 3.

2. Step 2: Check other options for correctness

   ^ is bitwise XOR, ^^ is invalid syntax, and pow() is not a built-in function in JavaScript.

3. Final Answer:

   5 ** 3 -> Option A

4. Quick Check:

   Power operator = ** [OK]

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

Common Mistakes:

• Using ^ instead of ** for power
• Trying to use pow() like in other languages
• Typing invalid operators like ^^

3. What will be the output of the following code?

console.log(10 % 4);

medium

A. 6

B. 0

C. 2

D. 4

Solution

1. Step 1: Calculate 10 divided by 4

   10 divided by 4 is 2 with a remainder of 2.

2. Step 2: Understand the % operator

   The % operator returns the remainder, so 10 % 4 equals 2.

3. Final Answer:

   2 -> Option C

4. Quick Check:

   10 % 4 = 2 [OK]

Hint: Remainder is what's left after division [OK]

Common Mistakes:

• Confusing remainder with quotient
• Thinking % does division
• Choosing 0 or 4 as remainder incorrectly

4. Find the error in this code snippet:

let result = 5 **;
console.log(result);

medium

A. console.log syntax error

B. Using wrong operator for power

C. Variable name 'result' is invalid

D. Missing right operand for ** operator

Solution

1. Step 1: Check the power operator usage

   The power operator ** needs two operands, like 5 ** 2. Here, the right operand is missing.

2. Step 2: Verify other parts of the code

   The variable name and console.log syntax are correct, so no errors there.

3. Final Answer:

   Missing right operand for ** operator -> Option D

4. Quick Check:

   Power operator needs two numbers [OK]

Hint: Power operator needs number on both sides [OK]

Common Mistakes:

• Leaving out the second number after **
• Thinking variable names cause error here
• Assuming console.log is wrong

5. You want to split 100 candies equally among 6 kids and find how many candies remain undistributed. Which expression gives the number of leftover candies?

hard

A. 100 / 6

B. 100 % 6

C. 100 - 6

D. 100 ** 6

Solution

1. Step 1: Understand the problem

   We want the leftover candies after dividing 100 by 6, which means the remainder.

2. Step 2: Choose the correct operator

   The remainder operator % gives the leftover amount, so 100 % 6 is correct.

3. Final Answer:

   100 % 6 -> Option B

4. Quick Check:

   Leftover = total % number [OK]

Hint: Use % to find leftovers after division [OK]

Common Mistakes:

• Using / which gives quotient, not remainder
• Subtracting numbers directly instead of remainder
• Using power operator mistakenly