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?
Rs. 7.98
Rs. 8
Rs. 8.50
Rs. 9
Answer: Option
Explanation:

Total quantity of petrol
consumed in 3 years
= 4000 + 4000 + 4000  litres
7.50 8 8.50
= 4000 2 + 1 + 2  litres
15 8 17
= 76700  litres
51

Total amount spent = Rs. (3 x 4000) = Rs. 12000.

Average cost = Rs. 12000 x 51 = Rs. 6120   = Rs. 7.98
76700 767

Discussion:
93 comments Page 8 of 10.

Jeevankumar said:   2 decades ago
Explain answer in simple logic.

Dev said:   2 decades ago
Explain answers in short cut as much as possible.

Subhasmita said:   1 decade ago
Please solve this equation 4000(2/15+1/8+2/17) = ?

Arif islam said:   9 years ago
Thanks @Krishna.

Jeevan said:   9 years ago
Nice, thanks for the explanation @Arvind.

D Trimurtulu said:   10 years ago
I did not understand this way. Any other way to simplify this problem? Please explain me.

Akashay said:   10 years ago
Is there any shortcut to solve this problem?

Sandeep said:   10 years ago
Only for this question based upon the options.

Think generally for three years amount is same but the purchasing of petrol is different.

The average is approximately 8 rupees. But in the first year we are purchasing the oil with low price then we get more petrol with the same amount than the other years.

By observing this we get something more in the denominator (petrol quantity) so absolutely numerator value decreases very less than the average (rs. 8).

By seeing options we can say 7.9 is the answer.

Swaroopa said:   1 decade ago
Thank you all for the explanation.

Varma said:   1 decade ago
Why take 7.50 + 8 + 8.50 / 3 = 8?


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