# 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* - 2*y* = -60 .... (ii)

Solving (i) and (ii) we get: *x* = 100 , *y* = 80.

The required answer A = 100.

Discussion:

74 comments Page 2 of 8.
Hello said:
5 years ago

Where is Ramesh? The one who explained the previous question very simply in this same chapter.

(1)

Swathi hj said:
5 years ago

Why we take x-10 and y+10, can anyone tell me?

(1)

Prakash said:
5 years ago

Could you please explain this? I am not getting it.

Prakash said:
5 years ago

Could you please explain this? I am not getting it.

Sagar said:
5 years ago

Thanks @Naga invy.

Geetha said:
5 years ago

Please Explain the 2nd step.

Chandu said:
5 years ago

We have to only subtract 10 students from A ie;A-10=B (OR) A=B+10.

But how do you add 10 to A sub 10 from B at a time that means 20 students are sending to B from A.

A-10=B,

B-20=2B=>B=20,

A-10=20,

A=30.

But how do you add 10 to A sub 10 from B at a time that means 20 students are sending to B from A.

A-10=B,

B-20=2B=>B=20,

A-10=20,

A=30.

(1)

Sarvesh said:
5 years ago

Thank you @Naga.

Naga Invy said:
5 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

(2)

Saurya said:
5 years ago

Thank all for explaining.

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