Question

In a recent year, the number of $1 bills in circulation in the U.S. was about 7 billion.

If the number of $10 bills was 20% of the number of $1 bills, about how many $10 bills were in circulation?
a.
1.4 billion
c.
.5 billion
b.
5.6 billion
d.
10 billion

Answer 1

there were 7billion $1 dollar bills
and there were 20% of THAT MUCH $10 bills, how many $10 bills were there?

well, 20% of of THAT MUCH will be 20% of 7billion
\(\bf \textit{n% of m}=\cfrac{n}{100}\times m\implies 20\%\textit{ of }7billions\implies \cfrac{20}{100}\times 7billions\)

Answer 2

20% of 7 billion (the number of $1 bills) = the number of $10 bills in circulation. We can write:

.2*(7billion)=1.4 billion (this is the number of $10 bills in circulation)