Question

How would I convert 140km to miles if the only information I was given in the question is there are 5280 feet in a mile?

Answer 1

By having outsider knowledge.

Explanation:

You could know that a feet is roughly 30cm, or that an inch is roughly 2.5cm. And then make the appropriate conversion rate with the process drawn below.

That being said, you have no real reason to know this (unless your teacher told you this on an earlier class on something) so you should have been given this data along with the rest of the problem.

`30 cm -> 1 ft`
`10^5 cm -> x ft`

`30x = 10^5 -> x = 3333.3 ft`

`1 km -> 3 333.3 ft`
`140 km -> y ft`

`y = 466 662 ft`

`5280 ft -> 1 mi`
`466 662ft -> z mi`

`5280z = 466 662 -> z = 466662/5280`
`z = 88.38 mi`