If a radioactive isotope has a half life of 1,000 years, how long does it take for 3/4 of the original sample?

Answer 1

To get rid of half the sample takes 1000 years. Now we have half the original sample. To get rid of half of this sample takes another 1000 years. Now we have 1/4 of the original sample. This means that in 2000 years 3/4 of the original sample has decomposed.

This answer is assuming that the question is asking for the time for 3/4 of the original sample to decompose.

Answer 2

The half life of a isotope is the time that a isotope takes to discompose half of it. So if we have 100 grams of the isotope with half life of 1000 years, it will take 1000 years to become 50 grams of that isotope, & therefore, 2000 for becoming 25 gram (thats 1/4 of the original sample left, that is 3/4 of the sample discomposed)

Answer 3

????? It seems you didn't ask your complete question. If you are asking how long it takes for 3/4 of the original sample to decay, the answer is 2,000 years (1/2 would be gone after 1,000 years, and 1/2 of the remainder [1/4] would be gone after another 1,000 years.

Answer 4

2000 years........

in 1000 years 1/2 of the sample will be gone. It will take another 1000 years for half of the remaing half to decay. At that point 3/4 of the original sample will be gone.

Answer 5

you've responded your self, the 0.5-life is the time it takes for 0.5 of the isotope to decay into the daughter product, four hundred tens of millions years 50% of the isotope often is the daughter isotope, then after yet another four hundred million years 0.5 of the make sure isotope will decay to the daughter - 800 million years seventy 5% of the isotope could have decayed to the daughter isotope. Make experience? wish this helps.

Answer 6

We can also use mathematics :]

an=a1 x q^n-1

So... q=1/2 an=100/4=25
a1=100 (grams for example)

25=100 times (1/2)^x

25/100=(1/2)^x

1/4=(1/2)^x

(1/2)^2=(1/2)^x

2=x

an=a3 cause x=n-1.
2 x 1000=2000 :D