Dimensional analysis

Question

The amount of fresh water on earth is estimated to be 3.73x108km3. There are 1000L in a cubic meter. How many 20,000 gallon backyard swimming looks can you fill up with this volume of freshwater? (3.785 litres = 1 gallon)

Answer 1

Whenever we do dimensional analysis, we start with what we know. Here, that is 3.73 x 10⁸ cubic kilometers.

Next, we need to be sure we understand where we want to end up. Here, we want our units of measurement in the answer to be in the number of backyard swimming pools.

OK. Now we can solve this problem.

3.73 x 10⁸ km³ x (1 x 10⁹ m³) / 1 km³ x 1000 L / 1 m³ x 1 gallon / 3.875 L x 1 swimming pool / 20,000 gallons = 4.8129032 x 10¹⁵ = 4.81 x 10¹⁵ swimming pools

I hope this helped.