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Maths Help- KS3

Posted: Mon Dec 02, 2013 2:04 pm
by rejim2
Hello all,

Any help much appreciated!

Question-
The yearly change in the yield of one particular crop in our area over the past 2 years was 20% increase followed by 20% decrease. What is the total percentage change over two years?

Thanks,

Re: Maths Help- KS3

Posted: Mon Dec 02, 2013 2:12 pm
by Ladymuck
Start with 100.
20% increase in year 1 gives you 120.
20% decrease is year 2 gives you a decrease of 24, so net result of 96.

In maths terms, I would describe the change as (1+.2)*(1-.2)=.96, so a total chance of 1-.96= a reduction by 4%

Re: Maths Help- KS3

Posted: Mon Dec 02, 2013 2:16 pm
by rejim2
Thankyou Lady muck! great... the choice answers were
-4%, -1% , 0% , 1% and 4%.