Originally Posted by
tjnguyen Ok i made a post about this on the pre-calc forum but I am in a hurry to get these checked because i have a exam tomorrow.
6) The radioactive isotope uranium 235 has a half-life of 8.8x10^8 years.
A) How much of a 1-gram sample will decay after 1000 years?
B) How long will it take for 90% of the mass to decay?
7) A bacteria culture is known to grow at a rate proportional to the amount present. After 1 hour, 1000 bacteria are present and after 4 hours, 3000 bacteria are present.
A) find an expression for the number of bacteria at any time T.
B) Find the number of bacteria that will be present after 5 hours.
C) When will the population reach 20,000?
D) How long does it take for the population to triple?
I did these out and i want to check my answers with anyone here
My answers:
6a) .99 or ~1
6b) 2.9x10^9 years
7a) Q(t)=1000e^(ln3/3)t
b) 6240 bacterias after 5 hours
c) 8.18 hours
d) 3 hours
thank you a lot