RRB JE Maths Important Solved MCQs

 

X and Y can do a piece of work in 20 days and 12 days respectively. X started the work alone and then after 4 days Y joined him till the completion of the work. How long did the work last?

A.

6 days

B.

10 days

C.

15 days

D.

20 days

Answer: Option B

 

 

Work done by X in 4 days =

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

1

x 4

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

=

1

.

20

5

 

Remaining 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

=

4

.

5

5

 

(X + Y)'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

=

8

=

2

.

20

12

60

15

 

Now,

2

work is done by X and Y in 1 day.

15

 

So,

4

work will be done by X and Y in

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

15

x

4

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

= 6 days.

5

2

5

Hence, total time taken = (6 + 4) days = 10 days.