if 36 men can do a piece of work in 5 hours , in how many hours will 15 men do it ?
"explanation : let the required no of hours be x . then less men , more hours ( indirect proportion ) \ inline \ fn _ jvn \ therefore 15 : 36 : : 5 : x \ inline \ fn _ jvn \ leftrightarrow ( 15 x x ) = ( 36 x 5 ) \ inline \ fn _ jvn \ leftrightarrow \ inline \ fn _ jvn x = \ frac { 36 \ times 5 } { 15 } = 12 hence , 15 men can do it in 12 hours . answer : a ) 12"
divide(multiply(36, 5), 15)