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Math Help - Percentage Problem

  1. #1
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    Question Percentage Problem

    Can someone please help me out with the following problem?

    If the price of petrol increases by 25%, by how much must a user cut down his consumption so that his expenditure on petrol remains constant?

    Thanks,

    Ron
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  2. #2
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    you have old_spending * 1.25 = new_spending_required_for_old_level

    and old_spending_with_return = old_spending / new_spending_required_for_old_level = 1/1.25

    the later is your result. (or better to say: 1- 1/1.25)
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  3. #3
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    Sorry but couldn't understand your explanation. Can you please explain in an easier way? Why have you done

    old_spending * 1.25 = new_spending_required_for_old_level

    Thanks,

    Ron
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  4. #4
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    Maybe follow this line of thought.

    Lets say $10 used to buy you 8 litres of petrol.

    Now with a 25% increase implies $12.50 will now buy you 8 litres of petrol. You need to know how many litres to buy at the new price such that you are still only spending $10.

    So 8 litres at $12.50 is $1.56 a litre.

    So you need to know $1.56 by X (litres) = $10

    Any better?
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  5. #5
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    OK....understood but how do you get the answer as 20%?

    Thanks,

    Ron

    OK...I got it....so he will be using 6.4 litres after price increase which means he will have to decrease consumption by (8-6.4)=1.6 litres which means (1.6*100)/8=20%
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