Set this up as
10 = 40 (1/2)t/28
and solve for t in years.
10/40 = (1/2)t/28
log(0.25) = (t/28) log(0.5)
t = 28 log(0.25) / log(0.5) years = 56 years
Test the answer:
56 years = 2(28 years) = 2 half-lives, so the remaining amount should be 1/2 of 1/2 of the initial amount, i.e. 1/4 of the initial amount, and 10 mg = 1/4 of 40 mg.
dinos were probably around pangea, the movement of land would be my guess lol
The answer is the Midwest
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Seems very basic, the ocean is above the plate, the plate material is heavier than water (it being rock). That's pretty much all of it. The plates grind a little and new land pushes up at plate boundaries but this does not seem to be related. The heavier material is below and the lighter above, those being rock and water respectively.
