Question

Mohan can repair an Instrument in 40 hours. Ram can repair the same instrument in 30
hours. Mohan and Ram work together to repair the same instrument for 8 hours. Then,
Mohan goes away. The number of hours that Ram takes to complete the work is (in hours)

Answer 1

mohan =1/40

ram =1/30

mohan+ram together =1/40 +1/30 =7/120

together work for 8 hours

7/120*8=7/15

remaining work =7/15 -1 =8/15

after ram only do the work  so

8/15*30=16 (correct anwser)