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aeon86

(2) The sum of the squares of the radii is 100.
this basically tells us that R1^2 + R2^2 = 100
a quick listing gives us only 2 possible combinations

R1 = 6 and R2 = 8
or
R1= 8 and R2 = 6

since the question is asking us about the total surface area, it doesn't matter which circle is largest since both cases result in the same total area.

don't get fooled into thinking you need (1) to limit the number of cases to 1

Be careful with this reasoning. 6 and 8 / 8 and 6 definitely aren't the only possible combinations. That's because the problem text never says that the radii have to be integers. For instance, R1 = sqrt(50) and R2 = sqrt(50) is a perfectly valid combination.

However, no matter what, as long as the sum is 100 the sum of the areas will be the same. That's because the area of a circle is pi(r^2), so the area of both circles is pi(R1^2) + pi(R2^2) = pi(R1^2 + R2^2) = 100pi.
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