Question

7. A, B and C together can do a piece of work in 15 days. B alone can do it in 30 days and
C alone can do it in 40 days. In now many days will A alone do the work?​

Answer 1

Step-by-step explanation:

Given,

(A+B+C) can do a piece of work in = 15 days

(A+B+C)’s 1 day work =151

B alone can do a piece of work in = 30 days

B’s 1 day work =301

C alone can do a piece of work in = 40 days

C’s 1 day work =401

So, 

A’s 1 day work =151−301+401

=151−1204+3=151−1207=1208−7=1201

∴ A can do a piece of work in 120 days.

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Answer 2

Answer:

Given,

(A+B+C) can do a piece of work in = 15 days

(A+B+C)’s 1 day work =

15

1

B alone can do a piece of work in = 30 days

B’s 1 day work =

30

1

C alone can do a piece of work in = 40 days

C’s 1 day work =

40

1

So,

A’s 1 day work =

15

1

−

30

1

+

40

1

=

15

1

−

120

4+3

=

15

1

−

120

7

=

120

8−7

=

120

1

∴ A can do a piece of work in 120 days.

Step-by-step explanation:

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