# Math. easy?

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On his 13th birthday he was 112cm tall and on his 14th birthday he was 121cm tall. Assume a geometric monthly growth rate. What is this rate?

I just need to know how to set it up. Please and thanks

• Math. easy? -

let the monthly rate be r

then 112(1+r)^12 = 121
(1+r)^12 = 1.080357..
take 12th root

1+r = 1.0064618
r = .0064618 --- monthly rate

BTW, I answered this question for somebody yesterday, perhaps it was you.
In that solution I missed the "monthly" part and took it as an annual rate

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