If 5 men or 9 women can do a piece of work in 19 days, then in how many days will 3 man and 6 women do the same work ?

A 12

B 15

C 18

D 21

Correct Answer: Option B

Solution: Short method: Time =( men₁ \( \times \) Women₁ \( \times \) Time₁ )/ (Men₁ \( \times \) Women₂ + Men₂ \( \times \) Women₁ )

= 5 \( \times \) 9 \( \times \) 19 / 5 \( \times \) 6 + 3 \( \times \) 9 = 15