Aptitude - Simplification - Discussion

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

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.

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

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)


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

The required answer A = 100.

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.

To solve equations:

(A part) (B part)
x + 20 = 2(y - 20)
20 candidates are sent from B to A,so we are adding 20 to x,and because we are sending 20 students to A it gets doubled(A=2B).
And
For solving equations just subtract both.

x - y = 20 .... (i)

x - 2y = -60 .... (ii)

You will get y=80 and then substitute in eq(i) you will get x=100.

Please explain me, how to solve (i) & (ii) and how get x=100 & y=80?

When 20 students sent from B to A,

Then A become twice then of B.

Thats The Reason We take 2 in the second step.

Then the number of students in A is double the number of students in B" so the step was look like 2(x+20) = (y-20). Then how it come(x+20) = 2(y-20).

x-y = 20 ------------(1).
x-2y = -60 ------------(2).

Solving (1) - (2),

x -y = 20----(1).
x -2y = -60----(2).
---------------
y = 80.
---------------
(If you want to solve two equations in any problem you must change sing of (2)nd equation without fail.)

Now you substitute the y value in (1)st or (2)nd equations as you like then you will get the value of x as 100.

x - y = 20-----(1).
y = 80.

so, x - 80 = 20.
x = 20+80.
x = 100.

Now you got it @Selvi.