Answer:
56 days
Explanation:

where A is final amount, Ao is initial amount, t is time taken, h is half life
Here given:
initial amount: 400 millicuries
final amount: 3.125 millicuries
half life: 8 days
time taken: ?
Hence solve for time taken:

<u>insert values given</u>

<u>divide both sides by 400</u>

<u>apply exponent rule</u>
<u />
<u>simplify</u>

<u>multiply both sides by 8</u>

Answer:
b = 2A/h - a . (option a)
Step-by-step explanation:
Check attachment
.05 *.07 = .0035
I assumed you forgot the decimal point
.05 * 07 = .35
0.8 *0.3 =.24
Answer:
a cross-section
Step-by-step explanation: