If the half-life of k-40 is 1.3 billion years and if a sample rock found on an island is estimated to be 1 billion years old, what percentage of the original parent k-40 would be present in the rock? round your numerical values to the hundredths decimal place.

answer choices

(a) 76.92%
(b) 1.3%
(c) 58.67%
(d) 99.99%

For this case, we must make a rule of three, to find the percentage of the k-40 found in the sample found.

1.3 ----------> 100%

1 -------------> x

Where "x" represents the percentage of k-40 present in the sample found.

Rounding off we have:

76.92%

Option A

step-by-step explanation:

i'm pretty sure it would take 20 hours because it's half the men so you multiply the number of hours it takes by 2