Until loop in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of an until loop counting down

What is the output of this Ruby code using an until loop?

Ruby

count = 3
until count == 0
  puts count
  count -= 1
end

A

1
2
3

B

0
1
2
3

C

3
2
1
0

D

3
2
1

💡 Hint

Remember, until runs the block while the condition is false.

The loop runs while count == 0 is false. It starts at 3 and decreases until it reaches 0, printing 3, 2, and 1.

❓ Predict Output

intermediate

Until loop with break condition inside

What will this Ruby code print?

Ruby

i = 0
until i > 5
  puts i
  break if i == 3
  i += 1
end

A

0
1
2
3
4
5

B

0
1
2
3

C

0
1
2
3
4

D

1
2
3

💡 Hint

The break stops the loop early when i is 3.

The loop prints i starting at 0. When i reaches 3, the break stops the loop, so it prints 0 to 3.

🔧 Debug

advanced

Identify the error in this until loop

What error does this Ruby code produce?

Ruby

count = 5
until count = 0
  puts count
  count -= 1
end

A Infinite loop

B SyntaxError

C TypeError

D No error, prints 5 to 1

💡 Hint

Check the condition in the until statement carefully.

The condition uses = (assignment) instead of == (comparison). This assigns 0 to count every time, so the condition is always false, causing an infinite loop.

🧠 Conceptual

advanced

Understanding until loop condition logic

Which statement best describes how an until loop works in Ruby?

A It runs the loop while the condition is true.

B It runs the loop until the condition becomes true.

C It runs the loop while the condition is false.

D It runs the loop only once regardless of the condition.

💡 Hint

Think about the opposite of a while loop.

An until loop runs while its condition is false. It stops when the condition becomes true.

❓ Predict Output

expert

Complex until loop with nested condition

What is the output of this Ruby code?

Ruby

x = 1
until x > 10
  if x % 3 == 0
    puts x
  end
  x += 2
end

A

3
6
9

B

3
9

C

3
9
15

D

6
9

💡 Hint

Check which values of x are multiples of 3 as it increases by 2.

The loop starts at 1 and adds 2 each time: 1, 3, 5, 7, 9. Only 3 and 9 are divisible by 3, so only those print.