For loop (rarely used in Ruby) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple for loop

What is the output of this Ruby code using a for loop?

Ruby

for i in 1..3
  puts i * 2
end

A

2
4
6

B

1
2
3

C

1
4
9

D Error: SyntaxError

💡 Hint

Remember the for loop iterates over the range 1 to 3 and multiplies each by 2.

The for loop goes through numbers 1, 2, and 3. Each number is multiplied by 2 and printed, so the output is 2, 4, and 6 each on a new line.

❓ Predict Output

intermediate

For loop with array iteration

What will this Ruby code print?

Ruby

arr = ['a', 'b', 'c']
for letter in arr
  print letter
end

A ['a', 'b', 'c']

B Error: undefined method 'print'

C a b c

D abc

💡 Hint

The print method outputs without newlines or spaces.

The for loop goes through each element in the array and prints it without spaces or newlines, so the output is 'abc'.

❓ Predict Output

advanced

For loop with break statement

What is the output of this Ruby code?

Ruby

for i in 1..5
  break if i > 3
  puts i
end

A

1
2
3
4
5

B

1
2

C

1
2
3

D Error: break outside loop

💡 Hint

The break stops the loop when i is greater than 3.

The loop iterates i from 1 to 5. For i=1,2,3: i > 3 is false, so puts i. For i=4: i > 3 is true, break before puts i. Output is 1 2 3 .

❓ Predict Output

advanced

For loop variable scope

What is the value of variable x after this Ruby code runs?

Ruby

x = 10
for x in 1..3
  # loop body empty
end
puts x

A Error: variable scope conflict

B 3

C 1

D 10

💡 Hint

In Ruby, the for loop variable reassigns the outer variable.

The for loop assigns x to 1, then 2, then 3. After the loop, x keeps the last value 3.

🧠 Conceptual

expert

Why is for loop rarely used in Ruby?

Which reason best explains why the for loop is rarely used in Ruby?

A Because Ruby prefers using iterators like each which have better variable scope handling

B Because for loops do not support ranges in Ruby

C Because for loops are slower than while loops in Ruby

D Because for loops cause syntax errors in modern Ruby versions

💡 Hint

Think about how Ruby handles variables inside loops.

Ruby prefers iterator methods like each because they create a new variable scope, avoiding side effects on outer variables, unlike for loops which reuse the outer variable.