Question

Karan and Arjun can do a piece of work in 24 days and Karan alone can do it in 120 days. Find the number of days taken by Arjun alone to complete a work.
1. 20 days
2. 30 days
3. 40 days
4. 60 days

Answer 1

Correct Answer - Option 2 : 30 days

Given

Karan and Arjun completes a work in 24 days

Karan completes a work in 120 days

Calculation

Let the work done by Arjun is x days

Work done by Karan and Arjun in 1 day = 1/24

Work done by Karan in 1 day = 1/120

Work done by Arjun in 1 day = 1/x

(1/120) + (1/x) = (1/24)

⇒ (1/x) = (1/24) - (120)

⇒ (1/x) = (5 - 1)/120

⇒ (1/x) = 4/120

⇒ x = 30 days

∴ Arjun completes a work in 30 days