Question

A 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 :

Answer 1

A can do the work in 15 days

⇒ 1 day = 1/15 of the work

B can do the work in 20 days

⇒ 1 day = 1/20 of the work

A and B work together:

1 day = 1/15 + 1/20 = 7/60 of the work

4 days = 7/60 x 4 = 7/15 of the work

Find the work that remain:

Work remain = 1 - 7/15 = 8/15

Answer; There is still 8/15 of the work to be done

Answer 2

Answer is 8/15
Because A = 1/15
B = 1/20
1/15+1/20= 4/60+ 3/60 ( LCM is 60)

7/60 x 4 = (We multiplied by 4 because in the question 4 days was given...so...when 60 and 4 cuts it equals to 15...so 15 is taken as denominator)
7/15
(1= 15/15)
15/15 - 7/15
= 8/15
So 8/15 fraction of work is left
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