Answer:Three major groups of islands in the Pacific Ocean are Melanesia, Micronesia and Polynesia.
Explanation:
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.
The circle with diameter of 24 means that 2

r = 24.
Solving for r, we get

r=24.
Dividing both sides by

, we get r=24/

.
The area of the full circle is

times 24 squared over

. The

being multiplied cancels out, meaning that 24 squared over

is the area of the full circle. 24 squared is 576, and dividing by 16 we get

as the answer.