FDP Flash Cards

[chris.hartline]

On the FDP Flash cards I believe there is a error in the explanation on card #4.

Answer: 20%
Start with a smart number. Assume the price of the
iPhone® is $100. 25% of 100 is 25, so the increased
price was $125. We know the sale then reduced the
price of the phone to its original price, $100, so the
sale reduced the price by $25, because 125 - 100 =
25. The percent decrease is the difference in prices
divided by the original price. 25/125 reduces to 1/5,
which is 20%.

I believe this is suppose to be "the difference divided by the increased price", which is 125. This will give you 20%.

Thanks

[StaceyKoprince]

Ah - I think that was a typo based on the author not noticing that the phrase "original price" was already used elsewhere in the problem to describe a different number. The standard formula for percentage change is:

Difference / original

where "original" = the starting point for that calculation

And the starting point for that final calculation, of course, is the $125 price. But it is definitely confusing to write the formula as "original" when the $100 figure was previously labeled the original price! I'll forward to our curriculum director - thanks!