How many half-lives have passed if the amount of parent isotope is 12.5%?

Three half lives.

Explanation:

Given data:

Number of half lives passed = ?

Amount of parent isotope left = 12.5%

Solution:

At time zero = 100%

At 1st half life = 100%/2 = 50%

At second half life = 50%/2 = 25%

At third half life = 25%/2 = 12.5%

It means three half lives would passed.

ch3 [ch2]14cooh

explanation:

(b) which contains higher levels of vitamin b, oranges or spinach?

explanation:

you can eliminate a, c, and d because they are questions based on opinions.