Posted by **Sue** on Saturday, August 14, 2010 at 6:57am.

Please help!!!

The mass of a particular substance is known to grow exponentially at a rate of 1.5% per day. Its initial mass was 230 grams and, after t days, it weighed 325 grams.

The equation modelling this growth is

230×1.015 t = 325.

Use the method of taking logs to solve this equation for t, giving your answer correct to the nearest day.

- Maths -
**Reiny**, Saturday, August 14, 2010 at 8:50am
I think you have a typo, and meant to say ...

230(1.015)^t = 325

(your equation would have a linear growth, not exponentially)

1.015^t = 325/230 = 1.4130435

log(1.015^t) = log 1.4130435

t = log 1.4130435/log 1.015 = 23.222

so it will take appr. 23 days.

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