SOLUTION: This is the last part of my homework and I am completely stumped on how to do exponents and logarithms. Please help me. It is 12:25am EST and I can not get this. Help me please!

Question 171742: This is the last part of my homework and I am completely stumped on how to do exponents and logarithms. Please help me. It is 12:25am EST and I can not get this. Help me please!
1. A cell divides into two identical copies every 4 minutes. How many cells will exist after 3 hours?
2. The level of thorium in a sample decreases by a factor of one-half every 4.2 million years. A meteorite is discovered to have only 7.6% of its original thorium remaining. How old is the meteorite?

Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
1. A cell divides into two identical copies every 4 minutes. How many cells will exist after 3 hours?
3hours = 180 minutes
180/4 = 45 divisions
Doubling at each division (4 mins) --> 2^45 in 3 hours.
2^45 = 3.51843721*10^13, = 35,184,372,100,000 cells
2. The level of thorium in a sample decreases by a factor of one-half every 4.2 million years. A meteorite is discovered to have only 7.6% of its original thorium remaining. How old is the meteorite?
7.6% = 0.076
0.076 = (1/2)^p p = periode, = 4.2 million years
log(0.076) = p*log(0.5)
p = 3.71786
Age = p*4.2 million = 15.614 million years

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