Question

4) The charred bones of a sloth in a cave in Chile represent the earliest evidence of human presence in the

Answer 1

Answer:

• about 8,880 years old

Explanation:

Half-life is the number of years it takes for a quantity of a substance to decompose in half.

You may measure the amount of the substance in mass, concentration, or activity, among others.

Thus, if you start with an amount A₀ of a substance that decays with a contstan half-life, the amount, A, remaining after passing n half-lives will be:

       $A=A_0\times \bigg(\dfrac{1}{2}\bigg)^n$

Then, if you know the initial amount,A₀, and the current amount remaining, A, of a substance, you can calculate the number of half-lives elapsed.

In this case:

• A = 5.22 disintegrations/minute·gram
• A₀ = 15.3 disintegratons/minut ·gram (when the organism was alive)

Thus:

• (5.22/15.3) = 0.34117647

• 0.34117647 = (0.5)ⁿ

• n × log(0.5) = log(0.34117647)

• n = log(0.34117647)/log(0.5)

• n = 1.5514

Hence, about 1.55 half-lives have elapsed since the organism died.

Since the half-life of C-14 is 5,730 years, the bones are 1.55 × 5,730 = 8,881.5 ≈ 8,880 years old ← answer.