Percentage increase calculation

[smiling bandit]

Bloody tacher forgot to mention we needed to know something for a test, so the sooner I get an answer the better. Plaese halp!

Basically, how do I figure percent increases?

Let's say I do my calculations and find that productivity increased from 127 units/input to 167 units/input. Or whatever.

Is the calc for percent change as follows?

167/127 = 1.31 ~ 131% (subtract 100% for base value = 31% increase

[pulykamell]

The equation is:

127 + 127x = 167
127x = 40
x = 40/127
x = 0.315

So the percentage increase is 31.5%

(edit: Or your way is quicker. You're saying 167 is 131% of 127, which essentially answers the same question, except you have to subtract the 1 at the end.)

[Santo Rugger]

Yes. Keep in mind that if the numbers were reversed, it wouldn't be a 31% decrease, though, it'd be a 127/167 = .76, 1-.76 = 24% decrease.

[Chessic Sense]

Change divided by origninal, or (new-old)/old. As was said above, the denominator must always be the old value, even when decreasing.

ETA: My favorite math rule, because it comes up everywhere- "Of means multiply". So if you say that something went up 35%, the complete statement would be "Jim added on 35% of his previous weight." or the "stock lost 25% of its value." Thus, it's Jimnew = Jimold +.35xJimold.

[smiling bandit]

Thanks. Where I get messed up is because I didn't know we needed it, and I forgot to take off the 100% base on my quickly-figured-out version. Fortunately, the test was administered so badly that the entire thing will be regiven. Now, if I can only figure what some of the more exotic terms meant.