the price of petrol has risen up by 20%.by how much percent must a driver reduce its consumption of petrol so as expense on it does not increases?
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If the price of petrol increases by 20%, by what percent should Mr. Brown reduce his consumption of petrol so that his expenditure on petrol remains the same?
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2 ANSWERS

Abhishek Yashodhara Shettigar, Mechanical engineer currently into Pollution control Mtech course
Answered Nov 16, 2017 · Author has 142answers and 111.4k answer views
To elaborate by an example, consider the cost of petrol as 70 rupees/ litre and Mr. Brown refills only 70 rupees petrol, no matter the increase or decrease in price.
Now if the cost is increased to 20% it will be
= 70+(20%*70)
=84 rupees/ litre.
So the price difference is 84–70=14 rupees/ litre.
Now if the expenditure should be same so that Mr. Brown will pay only 70 rupees, then he must be consuming less petrol. ( i.e lesser than 1 litre.). So he will consume :
i.e (70 rupees / 84 rupees)*1 litre= 0.8333 litre.
Reduction in quantity of petrol consumed by Mr. Brown= 1 litre –0.83333 litre= 0.1666 litre.
Therefore percentage reduction of petrol consumption by Mr. Brown
=(1–0.8333)*100= 16.67 %
OR
Simply (14/84)*100 = 16.66 %
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2 ANSWERS

Abhishek Yashodhara Shettigar, Mechanical engineer currently into Pollution control Mtech course
Answered Nov 16, 2017 · Author has 142answers and 111.4k answer views
To elaborate by an example, consider the cost of petrol as 70 rupees/ litre and Mr. Brown refills only 70 rupees petrol, no matter the increase or decrease in price.
Now if the cost is increased to 20% it will be
= 70+(20%*70)
=84 rupees/ litre.
So the price difference is 84–70=14 rupees/ litre.
Now if the expenditure should be same so that Mr. Brown will pay only 70 rupees, then he must be consuming less petrol. ( i.e lesser than 1 litre.). So he will consume :
i.e (70 rupees / 84 rupees)*1 litre= 0.8333 litre.
Reduction in quantity of petrol consumed by Mr. Brown= 1 litre –0.83333 litre= 0.1666 litre.
Therefore percentage reduction of petrol consumption by Mr. Brown
=(1–0.8333)*100= 16.67 %
OR
Simply (14/84)*100 = 16.66 %
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