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:
Answer: Option
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:
75 comments Page 3 of 8.
Shanthini said:
8 years ago
Friends I'll say one simple logic. If "is " is given after A then you must consider as A =. So as per question if we see means A is double the number of students in b.
So (x+20) =2 (y-20).
So (x+20) =2 (y-20).
Geetha said:
8 years ago
Assume A= 70 and B= 50.
Then according to question 10 students from A will be transferred to B so now they are going to b equal.
A=60 and B=60,
And if we transfer 20 students from B to A,
It's going to be A=80 and B=40 I.e A is double of B,
So why can't D answer be 80.
Then according to question 10 students from A will be transferred to B so now they are going to b equal.
A=60 and B=60,
And if we transfer 20 students from B to A,
It's going to be A=80 and B=40 I.e A is double of B,
So why can't D answer be 80.
Tuan said:
8 years ago
I don't understand this, please explain me.
Sreeram said:
8 years ago
See guys first take. x+10=2(y-40).
Then it comes as x-2y=-60,
First eq is x-y=20,
Solve both.
X-y=20,
x-2y=-60,
Change signs/
We get;
x-y=20,
-x+2y=60,
Then we get y=80,
Substitute in eq 1,
We get x=100.
Then it comes as x-2y=-60,
First eq is x-y=20,
Solve both.
X-y=20,
x-2y=-60,
Change signs/
We get;
x-y=20,
-x+2y=60,
Then we get y=80,
Substitute in eq 1,
We get x=100.
Temmy said:
8 years ago
How did they get the y=80?
Tuan Ossen said:
8 years ago
I don't understand, Please explain me with proper guidance.
Naidu said:
8 years ago
Why we have to change the signs could anyone please explain?
Hiranmoy said:
8 years ago
X-10 = y+10.
X-y = 10+10.
=20 (i).
Then, x+20 = 2(y-20)
x-2y = 40
x-y = 2x40
x-y = 80 (ii).
Now adding (i) &(ii) we get 20+80 = 100.
X-y = 10+10.
=20 (i).
Then, x+20 = 2(y-20)
x-2y = 40
x-y = 2x40
x-y = 80 (ii).
Now adding (i) &(ii) we get 20+80 = 100.
Prakash said:
6 years ago
Could you please explain this? I am not getting it.
Geethanjali said:
7 years ago
Simple to understand Thank you @Hiranmoy.
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