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 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.

Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.