Question

an element with mass of 630 grams decays by 18.8% per minute. How much of the element is remaining after 7 minutes.

Answer 1

Answer:

146.63 grams.

Step-by-step explanation:

The mass percent that remains after every minute is 100%-18.8 = 81.2% of the initial mass. This means after 1 minute the mass remaining is

$630*0.812$

After 2 minutes, the mass reaming is

$(630*0.812)*0.812$

After 3 minutes

$(630*0.812*0.812)*0.812$

so we see the general pattern: the grams remaining after $m$ minutes are

$\boxed{ 630 (0.812)^m}$

Now after 7 minutes the grams remaining are

$630(0.812)^7=146.63$

146.63 grams.