# Aptitude - Simplification - Discussion

Discussion Forum : Simplification - General Questions (Q.No. 2)
2.
There are two examinations rooms A and B. If 10 students are sent from A to B, then the number of students in each room is the same. If 20 candidates are sent from B to A, then the number of students in A is double the number of students in B. The number of students in room A is:
20
80
100
200
Explanation:

Let the number of students in rooms A and B be x and y respectively.

Then, x - 10 = y + 10      x - y = 20 .... (i)

and x + 20 = 2(y - 20)      x - 2y = -60 .... (ii)

Solving (i) and (ii) we get: x = 100 , y = 80.

The required answer A = 100.

Discussion:
74 comments Page 1 of 8.

Dear friend explain with example.........

I don't know how 2 was came at step 2.

I can't understand the sentence "then the number of students in A is double the number of students in B" explain me.

Assume x,y

x-a, y-b

10 students from b-a. So x-b,then y+b

Now doubled

2(y-20) then both equation solved.

Based on the answer a=100 and b=80. They said that if 20 sent from a to b then.

A will become double of b.

So if 20 sent then a=120 and b=60 i.e. a is double of b.

I can't understand the prasu explanation tell me clearly.