Arithmetic operators in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add two numbers and print the result.

Ruby

result = 5 [1] 3
puts result

Drag options to blanks, or click blank then click option'

A*

B-

C/

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using '-' subtracts instead of adding.

Using '*' multiplies instead of adding.

The + operator adds two numbers together.

2fill in blank

medium

Complete the code to multiply two numbers and print the result.

Ruby

result = 4 [1] 7
puts result

Drag options to blanks, or click blank then click option'

A+

B-

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+' adds instead of multiplying.

Using '/' divides instead of multiplying.

The * operator multiplies two numbers.

3fill in blank

hard

Fix the error in the code to correctly divide two numbers and print the result.

Ruby

result = 10 [1] 2
puts result

Drag options to blanks, or click blank then click option'

A/

B+

C-

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using '*' multiplies instead of dividing.

Using '-' subtracts instead of dividing.

The / operator divides the first number by the second.

4fill in blank

hard

Fill both blanks to calculate the remainder of division and print it.

Ruby

result = 17 [1] 5
puts result.to_s [2] " remainder"

Drag options to blanks, or click blank then click option'

A%

B+

C-

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using '-' or '*' instead of '%' for remainder.

Using '-' or '*' instead of '+' for concatenation.

The % operator gives the remainder of division. The + operator is used here to concatenate the result with a string.

5fill in blank

hard

Fill all three blanks to create a hash with keys as numbers and values as their squares, but only for numbers greater than 3.

Ruby

squares = (1..5).select { |[3]| [3] > 3 }.map { |[3]| [ [1], [2] ] }.to_h

Drag options to blanks, or click blank then click option'

Ax

Bx * x

Dy

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names inconsistently.

Using incorrect operators for multiplication.

We use x as the key, x * x as the value, and iterate with x over the range. The condition filters numbers greater than 3.

Practice

1. Which of the following is the correct symbol for multiplication in Ruby?

easy

A. -

B. *

C. +

D. /

Solution

1. Step 1: Recall basic arithmetic symbols in Ruby

   Ruby uses standard arithmetic symbols: + for addition, - for subtraction, * for multiplication, / for division.

2. Step 2: Identify the multiplication symbol

   The symbol for multiplication is the asterisk (*).

3. Final Answer:

   * -> Option B

4. Quick Check:

   Multiplication = * [OK]

Hint: Remember * means multiply in most languages including Ruby [OK]

Common Mistakes:

• Confusing + with multiplication
• Using / instead of *
• Using - instead of *

2. Which of the following Ruby expressions correctly calculates the remainder of 10 divided by 3?

easy

A. 10 - 3

B. 10 / 3

C. 10 * 3

D. 10 % 3

Solution

1. Step 1: Understand the modulus operator

   The modulus operator (%) returns the remainder after division.

2. Step 2: Identify the correct expression for remainder

   10 % 3 calculates the remainder when 10 is divided by 3, which is 1.

3. Final Answer:

   10 % 3 -> Option D

4. Quick Check:

   Remainder = % [OK]

Hint: Use % to get remainder after division [OK]

Common Mistakes:

• Using / instead of %
• Using * or - which do not give remainder
• Confusing % with division

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

result = 15 / 4
puts result

medium

A. 3

B. SyntaxError

C. 4

D. 3.75

Solution

1. Step 1: Understand integer division in Ruby

   When dividing two integers, Ruby performs integer division, discarding the decimal part.

2. Step 2: Calculate 15 divided by 4 as integer division

   15 / 4 equals 3.75, but integer division returns 3.

3. Final Answer:

   3 -> Option A

4. Quick Check:

   Integer division truncates decimals = 3 [OK]

Hint: Integer division drops decimals unless floats used [OK]

Common Mistakes:

• Expecting float result without floats
• Confusing / with %
• Thinking output is 4 or 3.75

4. Identify the error in this Ruby code snippet:

num = 10
result = num / 0
puts result

medium

A. Division by zero error

B. Syntax error due to missing operator

C. No error, output is 0

D. Variable 'num' is undefined

Solution

1. Step 1: Analyze the division operation

   The code divides 10 by 0, which is mathematically undefined.

2. Step 2: Understand Ruby's behavior on division by zero

   Ruby raises a ZeroDivisionError when dividing by zero.

3. Final Answer:

   Division by zero error -> Option A

4. Quick Check:

   Dividing by zero causes error [OK]

Hint: Never divide by zero; it causes runtime error [OK]

Common Mistakes:

• Thinking output is 0
• Assuming syntax error
• Ignoring runtime exceptions

5. You want to calculate the average of three numbers: 7, 8, and 9 in Ruby. Which expression correctly computes the average as a float?

hard

A. 7 + 8 + 9 / 3

B. (7 + 8 + 9) / 3

C. (7 + 8 + 9) / 3.0

D. (7 + 8 + 9) % 3

Solution

1. Step 1: Calculate sum of numbers

   Sum is 7 + 8 + 9 = 24.

2. Step 2: Divide by 3 as float division

   Dividing by 3.0 forces float division, giving 8.0 instead of integer 8.

3. Final Answer:

   (7 + 8 + 9) / 3.0 -> Option C

4. Quick Check:

   Use float divisor for float average [OK]

Hint: Divide by float (3.0) to get decimal average [OK]

Common Mistakes:

• Using integer division losing decimals
• Misusing % instead of /
• Wrong operator precedence without parentheses