Aptitude - Simplification - Discussion

They said the number of students in A is double the number of students in B. We should multiply A by 2 instead of multiplying B by 2. Why we are multiplying A by 2? Please tell me.

10 students moving from A to B


( decrease 10 from A & add 10 to B)
Then, A - 10 = B + 10 A - B = 20 .... (i)

20 Students moving B to A.(Note: After deducting 20 from B , A will be double) .

A + 20 = 2(B - 20)

A - 2B = -60 .... (ii)


====>

Solving (i) and (ii) we get: A = 100 , B = 80.

The required answer A = 100.

I didn't understand Solving (i) and (ii) we get: x = 100, why = 80. How?

Amigos..

Then the number of students in A is double the number of students in B.

Just use is equal to "=" instead of "is" After A and then think of it.

Easy isn't it.

Its simple given second condition that by sending 20 people A is twice of B so A+20=2(B-20) and solving both conditions we get 100

Take these two cases individually let us look first through options 1st option is 20 so to apply both conditions is not possible so come to 80 so given if 10 people are sent to b then people in both class rooms are same so definetly b will be 60.

So again now apply second condition individually so by sending 20 people 4rm b A is twice that of B so this condition is not satisfied so now take 100 and check then both conditions satisfy and hence ans is 100

Can you explain by assuming a = 100?

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

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.

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.