Question

Girish takes 28 seconds to assemble a cupboard .
Harish takes 21 seconds to assemble a similar cupboard. working together ,how long will both take to assemble 50 cupboards?

Answer 1

in one second girish do 1/28 of work and girish 1/21 of work
together in one second they do (1/28)+(1/21)
=1/12
so in one second they complete 1/12 of work...so it will take 12 second to assemble a cupboard together
so for 50cupboards it will take 50*12=600 seconds