Question

Four people can build a wall in 9 days. In how many days
can 12 persons build the same wall?

Answer 1

Answer:

If the number of workers decreases, the time to taken built the wall increases in the same proportion. Clearly, number of workers varies inversely to the number of days.

So here x1/y1 = x2/y2 where

x1 = 4 workers   y1 = 9 days

x2= 12 workers and y2=? days

Substitute, 4/12 = y2/9  ⇒ y2 = 4 × 9/12 = 3 days

Therefore 12 workers will build the same wall in 3 days.

Answer 2

Answer:

9/12*4=3

3 days is answer