Aptitude - Average - Discussion
Discussion Forum : Average - General Questions (Q.No. 9)
9.
A car owner buys petrol at Rs.7.50, Rs. 8 and Rs. 8.50 per litre for three successive years. What approximately is the average cost per litre of petrol if he spends Rs. 4000 each year?
Answer: Option
Explanation:
| Total quantity of petrol consumed in 3 years |
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Total amount spent = Rs. (3 x 4000) = Rs. 12000.
 Average cost = Rs. |
 |
12000 x 51 |  |
= Rs. | 6120 | = Rs. 7.98 |
| 76700 | 767 |
Discussion:
92 comments Page 8 of 10.
Raya said:
6 years ago
If you do (7.50+8+8.50)÷3 then you just get the avg per litre cost, but not the average of your spending.
In this question, we need to find the per lit avg cost of your spending you spend Rs 4000. Diff ppl have different avg per litre cost. It depends on how many litres you have used so hence we need to find the litre or amt you have consumed each year.
So, in the last step, we divide the total cost of 3 yrs by total amt of 3 years to GET THE PER LITRE COST OF 3 YEARS WHICH IS NOTHING BUT THE AVERAGE OF 3 YEARS.
In this question, we need to find the per lit avg cost of your spending you spend Rs 4000. Diff ppl have different avg per litre cost. It depends on how many litres you have used so hence we need to find the litre or amt you have consumed each year.
So, in the last step, we divide the total cost of 3 yrs by total amt of 3 years to GET THE PER LITRE COST OF 3 YEARS WHICH IS NOTHING BUT THE AVERAGE OF 3 YEARS.
Md. Sah-alam said:
6 years ago
Approximate cost should be 8.
Mohamed alfaan mirsha said:
6 years ago
I am not getting this, Can anyone explain me in detail?
Krishna said:
6 years ago
See at last everyone is asking why they have taken reciprocal. The answer is that in the question itself they asked what is the average cost per liter. So we have to find the cost of the amount of petrol not petrol at cost.
Karthik said:
5 years ago
You are correct, Thanks @Krishna.
Sai said:
5 years ago
Thanks @Krishna.
Sunil yadav said:
5 years ago
Thanks @Krishna.
Sagar said:
5 years ago
Thanks @Krishna.
Mansingh budha said:
4 years ago
I do not understand this problem. How can I solve it? please solve it again.
(1)
Sneha said:
4 years ago
= 4000( 100/750) + (1/8) + (100/850).
= 4000(2/15+1/8+2/17) cross multiplication,
= 4000(31/120+2/17) Cross mul,
= 4000(767/2040),
= 3068000/2040 decided by 4 on both side,
= 76700/51.
= 4000(2/15+1/8+2/17) cross multiplication,
= 4000(31/120+2/17) Cross mul,
= 4000(767/2040),
= 3068000/2040 decided by 4 on both side,
= 76700/51.
(2)
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