Question

The population of the US is about 3.02 X 10^8, and the average American uses about 1.5x10^2 gallons of water per day. Could this lake supply the American population with water for 1 day?

Answer 1

You need to supply the size of the lake in gallons.

Answer 2

At the very least you can calculate the gallons used in a day:
\[3.02*10^8*1.5*10^2=4.53*10^{10}\]
Applying the correct SF:
\[4.53*10^{10}\approx4.5*10^{10}\]