Question

A and b can complete a piece of work in 12 days and b and c together in 15 days. If a is twice as good workman as c, how long would he take to complete the same work by working alone?

Answer 1

a+b =12....1

c+b =15 ....2

2a=c        a = c/2

from 1 and 2 by (elemination method)

a+b=12

c+b=15

-   -   -

_______

a - c = -3

a - 2a = - 3

-a =-3

a=3  ans

Answer 2

Answer:

For A = 60 / 2 = 30 days

For B =20 days

For C = 60 /1 = 60 days

Step-by-step explanation:

A + B = 12 days

B + C = 15 days

Efficiency - A/C = 2/1

Therefore one day work for -

A = 2x and C = 1x

Let the total work be 60x ( LCM of 12 and 15)

One day work for -

A + B = 5x - (1)

B + C = 4x - (2)

Putting the value of A=2x in eq. 1

B = 3x

Now no. of days taken by B to complete the work = 60 / 3 = 20 days

For A = 60 / 2 = 30 days

For C = 60 /1 = 60 days