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ML Aggarwal Solutions Class 8 Mathematics Solutions for Direct and Inverse Variation Exercise 9.3 in Chapter 9 - Direct and Inverse Variation

Question 6 Direct and Inverse Variation Exercise 9.3

A and B separately do a work in 10 and 15 Solution: days respectively. They worked together for some days and then A completed the remaining work in 5 days.

how many days had A and B worked together?

Answer:

Given:

A can do a work in = 10 days

B can do a work in = 15 days

A’s, 1-day work = 1/10 …. (1)

B’s, 1 day work = 1/15

(A + B)’s 1 day work = 1/10 + 1/15

= (3+2)/30

= 5/30

= 1/6

Now, let us consider (A+B) worked together for ‘x’ days

So, (A+B)’s, x day work = x/6

Remaining work = 1 – x/6

It is given that,

A can do the remaining work, (1 – x/6) in = 5 days

So, A’s 1 day work = (1 – x/6)/5

= (6 - x)/(6×5)

= (6 - x)/30 ….. (2)

From (1) and (2), we get

1/10 = (6 - x)/30

30/10 = 6 – x

3 = 6 – x

x = 6 – 3

= 3

∴ Both A and B can do work together in 3 days

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