Question

Element X decays radioactively with a half life of 6 minutes. If there are 900 grams of

Element X, how long, to the nearest tenth of a minute, would it take the element to
decay to 121 grams?
y = a(.5)

Answer 1

17.4

Explanation:

Answer 2

t = 17.4 minutes

Explanation:

p = a(1/2)^(t/h)

121 = 900(1/2)^(t/6)

Divide both sides by 900

0.1344444444 = (1/2)^(t/6)

Take the log of both sides

log0.1344444444 = (t/6)log(1/2)

Divide both sides by log(1/2)

log0.1344444444 / log(1/2) = t/6

multiply both sides by 6

6 * log0.1344444444 / log(1/2) = t

use calculator

17.369507726516199 = t

rounded

t = 17.4 minutes