The half life of radioactive postassium is 1.3 billion years. If 10 grams are present now, how much will be present in 100 years?? 1000 years??
I said, amount now = amount intial / 2 ^ t/half life
so
10 / 2 ^ 100 / 1300000000 and got 9.99
then
10 / 2 ^ 1000 / 1300000000 and got 9.99
is this right???
please tell me where I went rightTHANKS
2007-07-30 08:50:22 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
Both are correct, if you are truncating at 1/100 gram. If you were rounding off, in both cases it would round up to 10.00 since the thousandths digit is also 9.
In n half-lives, 1/(2^n) portion of the original remains, so you are definitely using the right equation. If you went to more decimal places...
100 years : 9.999 999 467 grams remain
1,000 years : 9.999 994 668 grams remain
(I calculated those numbers using the same equation you used, but with a calculator that has about 20 digits' accuracy.)
2007-07-30 08:53:21 · answer #1 · answered by McFate 7 · 0⤊ 0⤋
Yes, you are right. The half life is so long that 100 or 1000 years makes little difference.
2007-07-30 15:53:56 · answer #2 · answered by yeeeehaw 5 · 0⤊ 0⤋
yes it's right. due to being such a small part of the half life
2007-07-30 16:03:53 · answer #3 · answered by bill45310252 5 · 0⤊ 0⤋