RRB JE Maths Important Solved MCQs

A can do a certain work in the same time in which B and C together can do it. If A and B together could do it in 10 days and C alone in 50 days, then B alone could do it in:

A.

15 days

B.

20 days

C.

25 days

D.

30 days

Answer: Option C

(A + B)'s 1 day's work =

1

10

 

C's 1 day's work =

1

50

 

(A + B + C)'s 1 day's work =

https://www.indiabix.com/_files/images/aptitude/1-sym-oparen-h1.gif

1

+

1

https://www.indiabix.com/_files/images/aptitude/1-sym-cparen-h1.gif

=

6

=

3

. .... (i)

10

50

50

25

A's 1 day's work = (B + C)'s 1 day's work .... (ii)

From (i) and (ii), we get: 2 x (A's 1 day's work) =

3

25

 

https://www.indiabix.com/_files/images/aptitude/1-sym-imp.gif A's 1 day's work =

3

.

50

 

https://www.indiabix.com/_files/images/aptitude/1-sym-tfr.gif B's 1 day's work

https://www.indiabix.com/_files/images/aptitude/1-sym-oparen-h1.gif

1

-

3

https://www.indiabix.com/_files/images/aptitude/1-sym-cparen-h1.gif

=

2

=

1

.

10

50

50

25

So, B alone could do the work in 25 days.