Question

if a man does work in 84 hours and it boosted his speed 5x only for 3 hours . In how many hours he complete work.​

Answer 1

time taken to finish a work=84hrs

work done in 1 hour=1/84

so in 1 hrs he speed become 5 times so =5/84

and it was for 3 hrs=5/84×3=5/28

so work done In 3hrs =5/28

and work left=28/28-5/38=23/28

which can be done in=23/28÷1/84=69hrs

so let's add the 2 times=69hrs+3=72hrs