21 labourers can build a wall in 25 days. If 14 additional labourers are employed, then in how many days the work can be completed ?

** Option:**

**A.**19 days

**B.**12 days

**C.**14 days

**D.**15 days

**Answer: D . 15 days**

** Justification:**

Original labourers = 21

Additional labourers = 14

Total labourers = 21 + 14 = 35.

21 labourers can build a wall in = 25 days.

1 labourers can build a wall in = 25 x 21 days.

35 labourers can build a wall in = ${25 × 21}/35$ = 15 days