Question

1) A men can do a work in 15 days and B in 20 days. If they work on it together for 4 days, then the

fraction of the work that is left is:

a) 1/4 b) 1/10 c) 7/15

d) 8/15 e) None of these​

Answer 1

Step-by-step explanation:

Take LCM of 15 and 20 as the total amount of work which is 60 units in this case.

A can do work in 15 days therefore amount of work done by A in 1 day is 60/15 = 4 units

B can do work in 15 days therefore amount of work done by A in 1 day is 60/20 = 3 units

Total amount of work done in 1 day =A work of 1 day+B's work of 1 day=4 units +3 units=7 units

Amount of work done in 4 days =4*7=28 units

Amount of Work Left = 60–28=32 units

Fraction of work left = Amount of work left/ Total Work = 32/60 = 8/15.

so the answer is d) 8/15

Answer 2

Answer:

Take LCM of 15 and 20 as the total amount of work which is 60 units in this case.

A can do work in 15 days therefore amount of work done by A in 1 day is 60/15 = 4 units

B can do work in 15 days therefore amount of work done by A in 1 day is 60/20 = 3 units

Total amount of work done in 1 day =A work of 1 day+B's work of 1 day=4 units +3 units=7 units

Amount of work done in 4 days =4*7=28 units

Amount of Work Left = 60–28=32 units

Fraction of work left = Amount of work left/ Total Work = 32/60 = 8/15.

Step-by-step explanation:

hope it helps you