IRB for interactive exploration in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this IRB session snippet?

Consider the following IRB commands entered one after another. What will be the output of the last command?

Ruby

x = 10
x += 5
x * 2

A 30

B 25

C 20

D 15

💡 Hint

Remember that x is first set to 10, then increased by 5, then multiplied by 2.

x starts at 10, then x += 5 makes it 15, then x * 2 equals 30.

🧠 Conceptual

intermediate

What does IRB stand for and what is its main purpose?

Choose the correct description of IRB in Ruby.

A Internal Ruby Builder, a compiler for Ruby programs.

B Interactive Ruby, a tool to write and test Ruby code line by line.

C Integrated Ruby Backend, a server for Ruby applications.

D Instant Ruby Binary, a Ruby executable file.

💡 Hint

IRB lets you try Ruby commands one at a time and see results immediately.

IRB stands for Interactive Ruby and is used to experiment with Ruby code interactively.

🔧 Debug

advanced

Why does this IRB code raise an error?

In IRB, the following code is entered: """ puts 'Hello """ What error will IRB show and why?

Ruby

puts 'Hello

A SyntaxError: unterminated string meets end of file

B NameError: undefined local variable or method `Hello'

C NoMethodError: undefined method `puts'

D TypeError: no implicit conversion of nil into String

💡 Hint

Check if all quotes are properly closed.

The string starting with a single quote is not closed, causing a syntax error.

📝 Syntax

advanced

Which IRB command correctly defines a method that returns the square of a number?

Select the correct Ruby method definition entered in IRB that returns the square of a given number n.

A

def square(n):
  return n * n
end

B

def square(n) {
  n * n
}

C

def square(n)
  n * n
end

D

def square n
  n * n
end

💡 Hint

Ruby methods use def and end keywords without colons or braces.

Option C uses correct Ruby syntax for method definition. Option C uses Python style colon and return. Option C uses braces like other languages. Option C misses parentheses which is allowed but less common and can cause ambiguity in IRB.

🚀 Application

expert

What is the value of variable result after this IRB session?

In IRB, the following commands are entered in order: """ arr = [1, 2, 3, 4] result = arr.map { |x| x * 3 }.select { |x| x > 6 } """ What is the value of result?

A [7, 8, 9, 10]

B [3, 6, 9, 12]

C [1, 2, 3, 4]

D [9, 12]

💡 Hint

First multiply each element by 3, then keep only those greater than 6.

Mapping multiplies each element by 3: [3,6,9,12]. Selecting elements > 6 keeps [9,12].