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:
76 comments Page 3 of 8.
Naga Invy said:
7 years ago
If 10 students sent from room A to B; then;
step 1: A -10 = B +10
Step 2 : If you change the B and -10 vice versa then the equation will be
A - B = 10 +10
therefore (A - B = 20) -----------------> Equation (1)
If 20 students sent from room B to A; then A becomes double as size of B
Step 3 : A + 20 = 2 (B - 20)
Please understand we are adding 2 in front of (B -20) because question states A becomes double as size B.
Now solve the step 3;
Step 4 : A + 20 = 2B -40
By changing the values vice versa, it becomes
Step 5 : A - 2B = (-20-40)
Step 6 A -2B = -60 -------------------> Equation (2)
Now solve both Equation 1 and 2
A- B = 20 ---------------> (1)
A- 2B = -60 ---------------> (2)
By changing the signs of equation 2, it becomes
A - B = 20 ---------------> (1)
- A + 2B = + 60 ---------------> (2)
----------------------
B = 80
---------------------
Solve the B value in equation ------> 1 to get an answer
A - B= 20.
then,
A - 80 = 20.
A = 20+80.
A = 100 ----------------> answer
step 1: A -10 = B +10
Step 2 : If you change the B and -10 vice versa then the equation will be
A - B = 10 +10
therefore (A - B = 20) -----------------> Equation (1)
If 20 students sent from room B to A; then A becomes double as size of B
Step 3 : A + 20 = 2 (B - 20)
Please understand we are adding 2 in front of (B -20) because question states A becomes double as size B.
Now solve the step 3;
Step 4 : A + 20 = 2B -40
By changing the values vice versa, it becomes
Step 5 : A - 2B = (-20-40)
Step 6 A -2B = -60 -------------------> Equation (2)
Now solve both Equation 1 and 2
A- B = 20 ---------------> (1)
A- 2B = -60 ---------------> (2)
By changing the signs of equation 2, it becomes
A - B = 20 ---------------> (1)
- A + 2B = + 60 ---------------> (2)
----------------------
B = 80
---------------------
Solve the B value in equation ------> 1 to get an answer
A - B= 20.
then,
A - 80 = 20.
A = 20+80.
A = 100 ----------------> answer
(5)
Saurya said:
7 years ago
Thank all for explaining.
Kaleem said:
7 years ago
Thank you all.
Nagesh v said:
7 years ago
Thank for you answer @Ash.
Garry said:
7 years ago
Accroding to last condtion, It should be 2(x+20).
Geethanjali said:
8 years ago
Simple to understand Thank you @Hiranmoy.
Srinu said:
8 years ago
Nice explanation. Thanks.
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.
Naidu said:
8 years ago
Why we have to change the signs could anyone please explain?
Tuan Ossen said:
8 years ago
I don't understand, Please explain me with proper guidance.
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