A 1.00-g sample of carbon from a modern

Question

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 half-life of carbon-14 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

Answer 1

15.3 dpmin x (60 min/hr) = 918 dphr which is slightly less than if it were the old sample. So something is a typo or the sample can't be very old.