Question

A and b can do a piece of work in 12 days b and c together can do it in 15 days if a is twice as good a workman as c find in what time b alone can do it

Answer 1

Answer:

Step-by-step explanation:

1/a+1/b=1/12

1/b+1/c=1/15

given 2a=c

put the value of c in eqn 2 we get

1/b+1/2a=1/15

then solve the eqn 1 & eqn 3 we get

a=30 b=20 c 60 ans is 20 days alone finish the work

Hope it helps you.....

Answer 2

B alone can do it in 20 days.

Step-by-step explanation:

Let one days word of A = 1/a

One days word of B = 1/b

One days word of C = 1/c

A and B can do a piece of work in 12 days.

$\dfrac{1}{a}+\dfrac{1}{b}=\dfrac{1}{12}$         .... (1)

B and C together can do it in 15 days.

$\dfrac{1}{b}+\dfrac{1}{c}=\dfrac{1}{15}$              .... (2)

A is twice as good a workman as C.

$\dfrac{1}{a}=2\times \dfrac{1}{c}$

From (1) and (2) substitute the values of 1/a and 1/c.

$\dfrac{1}{12}-\dfrac{1}{b}=2(\dfrac{1}{15}-\dfrac{1}{b})$

$\dfrac{1}{12}-\dfrac{1}{b}=\dfrac{2}{15}-\dfrac{2}{b}$

$\dfrac{2}{b}-\dfrac{1}{b}=\dfrac{2}{15}-\dfrac{1}{12}$

$\dfrac{1}{b}=\dfrac{8-5}{60}$

$\dfrac{1}{b}=\dfrac{1}{20}$

$b=20$

Therefore, B alone can do it in 20 days.

#Learn more

A is twice as good a workman as B and together they finish a piece of work in 18 days. In how many will A alone finish the work?

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