workbook pg 28 Cheetah

[jgray]

Greetings,
Could you explain in more detail how the cheetah would cost the same after a 25% increase and a 20% decrease?
pg 28 & 64 of the LGB Workbook.
thank you in advance.

[Dave Killoran]

Hi J,

It's because of the base number you start with when applying each percentage. When you start with 100, and then increase it by 25%, you add 25 and the result is 125.

Now, when you apply the 20% discount, you start with 125, the math changes because of that different starting point. 20%, or 1/5, of 125 is 25, so when you subtract that, you are back down to 100. Very tricky!

Please let me know if that helps. Thanks!

[jgray]

great, thanks. I didn't know I had to do actual math for this thing.
cheers

[LSAT99.9]

Hi,

Sorry to intrude, but on the LSAT does this show up frequently? If it does, would the numbers be simple so I could quickly do the math?

Thank you.

[Jonathan Evans]

Hi, LSAT99.9,

This kind of shifting percent increase verses percent decrease math is quite rare on the LSAT. However, knowing how to shift between numbers and percents is crucial. It is a near certainty that you would not be expected to do any math more complicated than what is described here.

For the purposes of preparing for the test, focus most of your attention on noticing the presence of numbers and percentages in a problem, recognizing what is being compared, and making note of the shifts that occur.

Essentially, numbers and percentages in comparisons lead to valid deductions only if the things being compared are equivalent in all important respects.

I hope this helps.