Aptitude - Average - Discussion

Discussion Forum : Average - General Questions (Q.No. 7)
7.
The average monthly income of P and Q is Rs. 5050. The average monthly income of Q and R is Rs. 6250 and the average monthly income of P and R is Rs. 5200. The monthly income of P is:
3500
4000
4050
5000
Answer: Option
Explanation:

Let P, Q and R represent their respective monthly incomes. Then, we have:

P + Q = (5050 x 2) = 10100 .... (i)

Q + R = (6250 x 2) = 12500 .... (ii)

P + R = (5200 x 2) = 10400 .... (iii)

Adding (i), (ii) and (iii), we get:  2(P + Q + R) = 33000  or   P + Q + R = 16500 .... (iv)

Subtracting (ii) from (iv), we get P = 4000.

P's monthly income = Rs. 4000.

Discussion:
93 comments Page 2 of 10.

Aarthi said:   1 decade ago
p+q = 5050.
q+r = 6250.
p+r = 5200.

We have to add this three equations P+q+q+r+p+r = 16500.

Then we get 2(p+q+r) = 16500.

p+q+r = 8250.
q+r = 6250.

We want to solve the above two equations then we get p = 2000.

For me the correct value is 2000.
(1)

Vinay said:   1 decade ago
P+Q = 5050*2 = 10100.
Q+R = 6250*2 = 12500.
P+R = 5200*2 = 10400.

P+Q + Q+R + P+R = 33000.

2P+2Q+2R = 33000.
2(P+Q=R) = 33000.

So, P+Q+R = 16500.

P+12500 = 16500. Because Q+R = 12500.

Hence P = 16500-12500 = 4000.

P+R = 10400.

R = 10400-4000 = 6400.

Q+R = 12500.

Q = 12500-6400 = 6100.
(1)

Pema wangcan said:   9 years ago
Its simple, what we have to do is concentrate on what was the logic behind the question see.

They have already given the average of PQ =5050, QR=6250 and PR=5200. But we have to see the income of P only, therefore average means individual share for P he has 5050 + 5200 = 10250.
But see here. The share of P was shared by both R and Q which means P has to get his share. And we have to deduct 6250. (10250 - 6250) = 4000.

Santosh said:   8 years ago
It's very Simple firstly do addition were p is present in question and subtract to were p is absent. Like P and Q is 5050 then P and are is 5200 add both 5050+5200= 10,250 then subtract to Q and are is 6250 then your answer will be 4000.

Ravi said:   8 years ago
Superb, thanks @Praveen.

Luciano said:   8 years ago
Why can't we take (5050+6250-5200)/2 = Q , Then use 5050 - Q = P?

SHIVA KUMAR said:   8 years ago
hi asmara

First avg income P+Q= 10100 {1}
Q+R= 12500 {2}
P+R= 10400 {3}

First adding eq 1 and 2 (P+Q)+(P+R) = 10100+10400 = 20500.
2P+Q+R= 20500 [4].
then subtract eq 4 and 2.
2P+Q+R-(Q+R ) = 20500-12500=8000.
2P =8000.
P = 4000.

Asmara said:   9 years ago
Why we subtract total from equation (ii) as that is a monthly income of Q+R. How we can assume it's P's monthly income while there is No written P, Please explain.

RECHU said:   9 years ago
SIMPLY
P + Q + R = 16500.
P + 12500 = 16500.
P = 16500 - 12500.
P = 4000.

SAM said:   9 years ago
Average of P and Q means (P + Q/2) = 5050.

Then it becomes, 2 goes that side.

P + Q = (5050 x 2) = 10100, Eq ---> (i).

Average of Q and R means Q + R/2.

Q + R = (6250 x 2) = 12500, Eq ---> (ii).

P + R/2.

P + R = (5200 x 2) = 10400, Eq ---> (iii).

Adding (i) , (ii) and (iii) , we get: 2 (P + Q + R) = 33000 or P + Q + R = 16500, Eq ---> (iv).

Subtracting (ii) from (iv), we get P = 4000.

P's monthly income = Rs. 4000.


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