Question

In 1943, the temperature in Rapid City, South Dakota, fell about 45 degrees in 5 minutes. What was the average drop in temperature per minute?

Answer 1

The average drop in temperature per minute is `9` degrees.

Explanation:

We know that it falls `45` degrees in `5` minutes, but we want to know the fall in `1` minute. So we set up a proportion.

First, let's set up 2 ratios and let's let `x` be the average drop in temperature per minute:
`45:5`
`x:1`

Now we can set up a proportion and do this thing called cross-multiplication:
`45/5 = x/1`

Cross multiplying is shown by this image:

So in our situation, it becomes
`45 = 5x`

We can divide both sides by `5` to get the value of `x`:
`9 = x`

The average drop in temperature per minute is `9` degrees.

Hope this helps!