Correct Answer - Option 2 : 25 days

**Given:**

M_{1} = 25

D_{1} = 10

H_{1} = 6

M_{2} = 18

H_{2} = 10

W_{2} = 3 × W_{1}

**Formula Used:**

(M_{1} × D_{1} × H_{1})/W_{1} = (M_{2} × D_{2} × H_{2})/W_{2}

Where M_{1} → Initial Men

D_{1} → Initial day

H_{1} → Initial hour

M_{2} → Final men

D_{2} → Final day

H_{2} → Final hour

**Calculation:**

(M_{1} × D_{1} × H_{1})/W_{1} = (M_{2} × D_{2} × H_{2})/W_{2}

⇒ (25 × 10 × 6)/W_{1} = (18 × D_{2} × 10)/(3 × W_{1})

⇒ (25 × 10 × 6 × 3 × W_{1})/(18 × 10 × W_{1})= D_{2}

⇒ D_{2} = 25

**∴ The time taken by 18 men to do 3 times of that work while working 10 hours per day is 25 days.**