Math CentralQuandaries & Queries


Question from Fred, a parent:

If I have $500 and it grew to $3,000, what is the correct description of the increase? Is it a sixfold increase (sextupled), or a fivefold increase (quintupled)?
When I divide $3,000 by $500, the result is six, therefore, a sixfold increase?

Hi Fred.

The word "increase" might make you wonder if you should divide $2500 by $500 rather than $3000 by $500, but really it is universally understood that the word is just part of the whole term "n-fold increase" and has no practical effect on the meaning.

When we say "the stock went up two-fold" or "it had a two-fold increase" or "it doubled", we are saying the same thing in all cases. A two-fold increase means the final amount is twice the original amount. So going from $500 to $3000 is a six-fold increase, because $3000/$500 is 6.

Don't let the word "increase" confuse you, just chalk it up to another one of the many peculiarities of the english language.

Stephen La Rocque.

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