Question

15 workers took 8 hours to build a wall. How many hours 12 workers need to build the same wall​

Answer 1

10hours

Let number of hours be x hours for 12 workers to build the same wall. The number of workers and the number of hours are in inverse variation. 15workers =8hours . so 12 workers =x hours . So 12 worker will require more hours than 15 workers to build the same wall. 15/ 12=8/x . = 15/12=x/8 (inverse variation) 12x=120 (cross multiply) x=120/12=10 . Therefore 10hours will be required for 12workers to build the same wall

Answer 2

Time -Work Problem

Number of workers who worked for 8 hours to build the wall $=15$

Number of hours 1 worker takes to build a wall$=15\times8=120$ hours.

Let 12 workers takes x hours to build a wall.

Hence, 1 worker will take $x\times12 \ hours$ to build the same wall.

According to question,

$120=x\times12\\\\\implies \frac{120}{12}=x\\\\\implies x=10 \ hours$

Hence, 12 works needs 10 hours to build the wall.