Working alone A can do a work in 72 days and B in 90 days. If they work on it together for 10 days,then what fraction or work is left?

Any method for finding it ?

3/4 th work is left

lcm of 72 and 90= 360, a' s one day work 360/72=5, b's one day work 360/90= 4 units in 10 days together 10(5+4)= 90, remaining units 270, which is 270/360 fraction= 3/4th of total work

Hi Sejal,
Consider that A and B make cakes. The work is to make 360 cakes(LCM of 72 and 90). Thus, individually A makes 5 cakes in a day and B makes 4 cakes a day. In 10 days they make 90 cakes. Hence fraction left is (360-90)/360 which is 3/4.

@Anugrah

A = 72 = 1.38( per day efficiency )
B = 90 = 1.11( per day efficiency )

1.38+1.11 = 2.49

so , 2.49* 10 = 24.9

24.9 - work complete out of 100

so , total 75 approx work is pending & 3/4 is the ratio of 75.