Correct Answer - Option 1 : 5 days

**Given:**

Ram can do a piece of work in 5 days

Sham can do the same in 10 days

Ram, Sham and Karan can do a together work in 2 days

**Concept used:**

Unitary Method

**Calculation:**

One day's work of Ram = 1/5

One day's work of Sham = 1/10

One day's work of Karan = [1/2 – (1/5 + 1/10)]

⇒ [1/2 – (2 + 1)/10]

⇒ (1/2 – 3/10)

⇒ (5 – 3)/10

⇒ 2/10 = 1/5

**∴ Karan to do the work in 5 days.**