Posted by Melody on Thursday, February 17, 2011 at 3:18pm.
How do I setup/solve this problem? Please help me.
The halflife of the radioactive isotope gallium70 is 20 minutes. If the initial amount of gallium70 is 25 milligrams, when will 10 milligrams be left?

calculus  Reiny, Thursday, February 17, 2011 at 5:36pm
can you solve
10 = 25(.5)^(t/20) where t will be in minutes ?

calculus  Melody, Thursday, February 17, 2011 at 5:48pm
This is what I got..
25(1/2)^(t/20)=10
(1/2)^(t/20)=10/25=2/5
(1/2)^(t/20)=2/5
t/20=log(2/5)/log(1/2)
t=20(log(2/5)/log(1/2))
t=26.44
Is this correct?

calculus  Reiny, Thursday, February 17, 2011 at 5:53pm
correct, good job.
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