Question

After three half- lives, a sample contains 10 grams of parent isotopes. How many grams of the parent isotope were present to start?

its not for biology..... its for Earth/Space Science

Answer 1

The answer is 80

Step-by-step explanation:

a half lives takes away half of an amount, in the question it said 3 half- lives.

the only posible answer is 80.

FIRST half lives: 80-40=40

SECOND half lives: 40-20=20

THIRD half lives: 20-10=10

80 is the only way to get to 10 with three half-lives.

Answer 2

Answer: Initial amount of parent isotope present in the sample was 80 grams.

Step-by-step explanation: Initial amount was= 80 grams

The sample undergone radioactive decay and after first half-life, it has= 40 grams (half of initial amount)

after second half-life, it has= 20 grams

And after third half-life, it has= 10 grams

Thus, the sample at present has 10 grams and initially had 80 grams of the parent isotope materials.