# There are 5 miles to 8 km. How many km in 80 miles?

Apr 15, 2018

$80 \text{ miles} = 128 k m$

#### Explanation:

Write a direct proportion to compare miles to Km.

5/8 = 80/x" "(larr " miles")/(larr" km")

You could decide what $5$ was multiplied by to give $80$ and do the same to the $8.$

5/8xx 16/16 = 80/128" "(larr " miles")/(larr" km")

Or Cross multiply to get:

$5 x = 8 \times 80$

$x = \frac{8 \times 80}{5}$

$x = 128$ km

OR Find a conversion factor:

$5 \text{ miles } = 8 k m$

$1 \text{ mile } = \frac{8}{5} k m$

$80 \text{ miles } = 80 \times \frac{8}{5} = 128 k m$