MathBench > Measurement

Follow the Units

The second challenge

Ben Bradlee: Bernstein, are you sure on this story?

Carl Bernstein: Absolutely.

Ben Bradlee: Woodward?

Bob Woodward: I'm sure.

Ben Bradlee: I'm not. It still seems thin.

Howard Simons: Get another source.

 


garage garage

Challenge Problem 2

An unlucky biology class is tasked with censusing rats in a parking garage. Based on remote photographs, they determine the average density of rats is 1.4 rats per parking space (1.5 by 5 meters). What is that in rats per square kilometer?




The first thing we need to do is to figure out what units we're dealing with. We could say the units are

1.4 rats / 1 parking space

but I'm pretty sure this one is not in the books. But we do know the width and depth of the parking space in meters, and that allows us to figure out the area of the space:

1.5m x 5m = 7.5m2

So, if I asked you, how many rats were there in how much space, you could say

there were 1.4 rats in 7.5m2, or

1.4 rats / 7.5m2, or

0.19 rats / 1m2

 

hummerGive it a try: Say you found 3 rats in a hummer space that was 3m by 6.2m. What was the density of rats (how many rats per how much space)?

(To make this problem interactive, turn on javascript!)

I think I have the answer: 3/18.6 = 0.16 rats/m2