# If a person smokes 10 packs of cigarettes a week and each cigarette contains 5.00mg of tar, how many weeks will the person have to smoke to inhale 0.25lb of tar?

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Borys Shumyatskiy | Certified Educator

Hello!

There is one unknown in this problem — how much cigarettes in one pack. I suppose this is 20, but let's denote this quantity as `n_p` .

During a week, a person smokes `10*n_p` cigarettes. Each cigarette contains 5 mg of tar so `10*n_p` cigarettes contain

`50*n_p` mg of tar = `0.05*n_p` g of tar (by week).

One lb is approx. 454g, so 0.25lb is 0.25*454 = 113.5 (g).

Now, divide the "desired" quantity of tar by its "speed" to obtain time:

`(113.5)/(0.05*n_p) = 2270/n_p` (weeks).

For `n_p=20` then `0.05*n_p=1` (g) and the answer is **113.5 weeks**, or slightly more than 2 years.

For `n_p=25` the answer is 2270/25=**90.8** (weeks).

You can compute the answer for any given `n_p.`