Hi JoAnne,

Suppose the question was

What is 50% of 500 billion dollars?

That you can do in your head, it's 250 billion dollars. This s easy since 50% is $\large \frac12$ and so

\[\mbox{ 50 % of 500 billion is } \frac12 \times 500,000,000,000 = 250,000,000,000.\]

Using the same reasoning, since 25% is $\large \frac{25}{100}$ and $25 \times 5 = 125,$ 25% of 500 billion is

\[\frac{25}{100}\times 500,000,000,000 = 1,250,000,000.\]

What about 2.5% of 500? Here 2.5% is

\[ \frac{2.5}{100} = \frac{2.5 \times 10}{100 \times 10} = \frac{25}{1000}\]

and hence 2.5 % of 500 is

\[\frac{25}{1000} \times 500,000,000,000.\]

Now try your problem,
Penny