Carbon dating
repeat exercise 19 for a piece of charcoal that contains 30% as much radioactive carbon as a modern piece.

Check explanation.

Step-by-step explanation:

The question given is not complete. But, what we really need is the value of half life for the piece of (carbon) charcoal. To solve this, we will ASSUME that that the half life is 6000 years. Before we we continue soving, let us take a look at some important terms from the question.

CARBON DATING: carbon dating is the technique used in determining the age of a material. Every living thing contain a certain amount of carbon-14 when they are still alive, but when living things die, the amount of carbon-14 decreases exponentially and the amount of carbon-13 is measured in dead matter.

HALF LIFE: Half life is the time taken for a quantity to decrease to half of its initial value.

So, let's proceed to solve the problem.

Step 1: find the number of half life that has passed.

From the definition of half life above, we say that;

(1/2)^x= 30/100. Where x is the number of half life that has passed.

So,

(1/2)^x = 0.3.

Take log of both sides.

Hence: x log 0.5 = log 0.3.

x = log 0.3/ log 0.5.

x= - 0.5229/ - 0.3010.

x= 1.74

Step 2: find the age of the charcoal.

Therefore, number of half life that has passed × half life given.

Age= 1.74 × 6000.

Age= 10,440 years

12

step-by-step explanation:

a triangle's   full angle is 180 degrees so 180 - 156 = 24. 24/2=12