For one thing, Cal and Martha are technically in agreement; 0.1 and 0.10 are the exact same value. To see whether they're right, or whether Angela had it correct, let's take a look at the numbers 0.5 and 0.2.
As fractions, those two values would be [tex] \frac{5}{10} [/tex] and [tex]\frac{2}{10}[/tex], or [tex] \frac{1}{2} [/tex] and [tex] \frac{1}{5} [/tex] when reduced. When you cut the original pizza in half, you cut it into 2 equal slices. Cutting each of those two pieces into 5 equal pieces, we get a total of 5 x 2 = 10 equal slices. So, taking one of those slices at that point - as Angela did - would be taking [tex] \frac{1}{10} [/tex] - or 0.1 - of the whole pizza.
So, both Cal and Martha are correct.
