A new acne medication guarantees a 16 percent decrease in acne every week it is used. If a teenager began with 50 pimples

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#1

A new acne medication guarantees a 16 percent decrease in acne every week it is used. If a teenager began with 50 pimples, how many weeks before he was down to fewer than 5 pimples?

Answer:

If a teenager only takes one pimple per day, the remaining is 50-7*7-X=1