# How many labourers of double the efficiency are needed to build 3 such walls in 5 days ?

6 labourers can build a wall in 10 days. How many labourers of double the efficiency are needed to build 3 such walls in 5 days ?

- 36
- 18
- 20
- 16

(6*10*1)/(5*2) = 6

3 such walls = 6*3 = 18