PWN the SAT Q&A • Can you go over #13 for test 4 section 9(pg 613) as well. Im having a lot of trouble with that one and the collegeboard explanation isnt helping either.

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Anonymous asked:

Can you go over #13 for test 4 section 9(pg 613) as well. Im having a lot of trouble with that one and the collegeboard explanation isnt helping either.

Many percent questions are easily conquered with plug in, and this one is no exception.

Start by assuming the original price of the phone is $100. It’s increased by 10%, so it becomes $110.

Then it’s decreased by 25%. 25% of $110 is $27.5, so the price drops to $110 - $22.5 = $82.5

Of course, this can also be solved with algebra. It’s just uglier:

$\frac{x+\frac{10}{100}x-\frac{25}{100}\left ( x+\frac{10}{100}x \right )}{x}\times100\%$

Simplify the above, and you’ll get 82.5%.