chemistry
posted by Eddy .
A 1.00g sample of carbon from a modern
source gave 15.3 disintegrations per minute. A sample of carbon from an “old” source gave 920 disintegrations per hour. What is the age of the “old” sample of carbon? The halflife of carbon14 is 5.73×103 year.
a. about 34,400 years
b. about 345,000 years
c. about 20 million years
d. less than a few years

Typo: The halflife is 5.7x10^3

Without even doing the math it the change in disintegrations is merely .03333, the sample must have decayed for
d. less than a few years 
whoops, i did the math and it came out to about 34,400 years. Sorry for my earlier answer

k = 0.693/t_{1/2}
k = 0.693/5.7E3 = 1.22E4
ln(15.3333/15.3) = 1.22E4(t)
t = about 18 year. 
vanden bout

actually drake was right on his first answer i had this question on my homework and it is d. less than a few years :)