let total work =600 units (LCM of 200 , 300 ) A does per day =
600
200
=3 units B does per day
600
300
=2 units Both A and B together work per day =5 units Let both A and B together work for x days and remaining done by A in 100days So, 5units×xdays+3units×100days=600 5x+300=600 ⇒x=60 days Where x is number of days B work with A