Question

Landen's front lawn measures 20 feet by 80 feet. He counts to find that there are

120 blades of grass per square inch. How many blades of grass are in the entire
lawn?

Answer 1

`27,648,000`

Explanation:

The area of a rectangle is given by
`l\cdot w`. Landen's 20 feet by 80 feet front lawn therefore has an area of
`20\cdot 80 = \fbox{$1600\: \mathrm{ft^2}$}`.

He counts there are 120 blades of grass per square inch. There are
`12^2=144` square inches in one square foot.

Therefore, his lawn has an area of
`1600\: \mathrm{ft^2}\cdot \frac{144\:\mathrm{in^2}}{1\:\mathrm{ft^2}}=230,400\:\mathrm{in^2}`.

Thus, there are
`230,400\:\mathrm{in^2}\cdot 120=\fbox{$27,648,000$}` blades of grass in the entire lawn.