Question

An element with a mass of 320 grams decays by 5.1% per minute. To the nearest tenth of a minute, how long will it be until there are 200 grams of the element remaining?

Answer 1

the answer is 9

Explanation:

answered on delta math and got it correct

Answer 2

5.1% - 0.051

Decay formula = total = start value x (1-rate)^time

200 = 320 x (1-0.051)^t

200 = 320 x 0.949^t

Divide both sides by 320"

0.625 = 0.949^t

Take the logarithm of both sides:

log 0.949^t = log 0.625

t * log 0.949 = log 0.625

t = log 0.625/log 0.949 = 8.98 minutes

Rounded to nearest minute = 9 minutes