Question

Ravi can do a price of work in 15 hour while Raman can do it in 12 hour how long will it take to do it working together

Answer 1

1/15+1/12=4+5/60
9/60=3/20

Answer 2

Ravi can do a piece of work in 15 hour

So in 1 hour =1/15


Similarly in 1 hour Raman =1/12

Therefore combine work in 1 hour =(1/15)+(1/12)
=9/60

so total time taken =60/9=20/3
$20 \div 3$
$6.67 \: hours$