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 3 of 10.
Smiley said:
1 decade ago
How it comes 2/15 + 1/8 + 2/17?
(1)
Sri said:
1 decade ago
Can't understand last calculation that why the reciprocal of the consumed quantity of the petrol is taken?
(1)
Ganapathy said:
1 decade ago
What about this.
1yr 7. 50 * 4000 = 30000.
2yr 8. 00 * 4000 = 32000.
3yr 8. 50 * 4000 = 34000.
Total = 96000.
Total amount spend for 3yrs = 4000*3 = 12000.
Avg amt spent for 3 years = 96000/12000 = 8Rs.
1yr 7. 50 * 4000 = 30000.
2yr 8. 00 * 4000 = 32000.
3yr 8. 50 * 4000 = 34000.
Total = 96000.
Total amount spend for 3yrs = 4000*3 = 12000.
Avg amt spent for 3 years = 96000/12000 = 8Rs.
(1)
Satya said:
7 years ago
It is very easy to understand. Thanks for solving @Krishna.
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.
Mohamed alfaan mirsha said:
6 years ago
I am not getting this, Can anyone explain me in detail?
Md. Sah-alam said:
6 years ago
Approximate cost should be 8.
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.
Shubham said:
6 years ago
In this equation,
= 4000(2/15+1/8+2/17),
= 76700/51.
= 4000(2/15+1/8+2/17),
= 76700/51.
Dokuparthi Brahmam said:
6 years ago
Thanks @Krishna.
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