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 5 of 10.

Bhanu said:   7 years ago
Thank you @Prabhjeet.

K L N Sarma said:   7 years ago
Guys, if you say p=4000, what will be your answers for Q and R.

My answer is p=2000, Q=3050, R = 3200
If we add all the 3 equations, we get 2 times (P+Q+R) = 16500. therefore, P+Q+R = 16500/2 = 8250.
8250 - (Q+R) = 8250-6250 = 2000.

Subhankar said:   7 years ago
5050+5200=1025, 10250-6250=4000.

Kheyali Chanak said:   8 years ago
It will be simple if apply (i)- (ii)+(iii) then we get 2P=8000, therefore P=4000.

Likhita said:   8 years ago
Thanks @Tarun it's very excellent explanation.

Bhavna said:   8 years ago
Very nice way explanation thanks @Tarun.

Sadhya said:   8 years ago
first i tell the procedure @Kalpana.
13*48 = 624
57 - 18 = 39
so 624 - 39 = 585.
585\13 = 45 answer.

Or tricky method here average is 48 but the person who has 57 is retired that means 57 - 48 = 9 this is the number reduced.in addition to this in place of 48 only 18 joined that means there is a decrease of 30.

Finally, the decrease of average is 30 + 9 = 39. 39/13 =3 . so 48 - 3 = 45 answer.

Prabhjeet said:   1 decade ago
p+q=10100..........eq 1
q+r=12500.........eq 2
p+r=10400...........eq 3

subtracting 2 from 1 we get,

p+q-q-r=10100-12500
p-r=-2400.......eq 4
adding eq3 to eq 4

p-r+r+p=10100+(-2400)

2p=8000
p=4000

Rite ans.

Siva said:   1 decade ago
2p=2(5050+5200-6250)
=>p=4000

Sana. said:   1 decade ago
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.

So why did we subtract from (ii) ?


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