Thomas R. answered • 05/11/18
Tutor
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Over 25 years of experience and a sense of humor about math
Well....okay, I 'll throw you a lifeline. Ready?
To find the percent increase or decrease, you must first make sure you actually have an increase or decrease, not just the percentage of it. You don't have it yet, but that presents no challenge:
135 - 54 = 81
Now we're ready to take on the problem, using the percent equation:
Part / Whole = % / 100
81 / 135 = X / 100
How did I know which numbers went where? Remember this rule:
"The change is the part and the whole is the start". The decrease is a change, so it goes on top. The 54 was written first, but in reality the $135 came first, falling later to $54. That makes it the start. We need only cross-multiply and then solve:
81 * 100 = 135 * X
8100 = 135X
8100 / 135 = 135X / 135
60 = X
In other words, the percent decrease is 60%
