Aptitude - Simplification - Discussion

I know everyone understood the first part, but in the second part, some might find difficult to understand why we are doubling in why part rather than the x part. Here is my view.

Read the question very very slowly.

Here they told, "If 20 candidates are sent from B to A, then the number of students in A is double the number in B". So x+20 = 2 (y - 20).

So for those who argue it should be 2 (x + 20) = y - 20, then the question would be below.

"If 20 candidates are sent from B to A, then the number of students in A is doubled (the remain details about B would have been ignored).

I hope it clear your doubts.

We can find out the answer by option if the 1st option is 80. Consider the student of class B and transfer 10 students then in both the class are equal so definitely, A class has a 100 student then tally it.

Exactly I have the same doubt as same as @Nandhakumar.

Can anyone help us?

If A is double then, Why 2 (y - 20)?

It is A which is double. So the equation should be 2 (x + 20) = y - 20. Right?

Friends you are doing upto x and why values. But we have to double the A also comparing to B.

If 10 students are sent from A to B,then the number of students in each room is the same
a-10 = b+10 ; ---- (1)

If 20 candidates are sent from B to A, then the number of students in A is double the number of students in B.
a+20 = 2(b -20); ---- (2) ( suppose A=10,B=5 that means A=2B then 10=10 )

Equation 1

a-10 = b+10.
a-b = 20.

Equation 2

a+20 = 2(b-20)
a+20 = 2b -40
a-2b = -60.


Solving equation 1 and 2
a-b = 20
a-2b = -60 (-a+2b = +60)
_____________.
b = 80

b is substitute in equation 1
a - b = 20
a = 20 + b
a = 20 + 80
a = 100

The answer is a = 100

I couldn't get how we solve both equation please make it clear by multiply.

Assume maximum capacity of both side 100 and subtract 20 from it a:b = 100:80.

It is very simple assume maximum capacity of seats in both room is 100, now A:B = 100:80.

There is no need to think about 1st equation or second just do maximum-lesser no. of side.