Step-by-step explanation:
There are 2 ways we can do this. We can use our friend which we will call a special device or we could actually solve using formulas we already know. Today, I will be using a formula but you can easily just use the secret device.
Step 1: Knowing the formula which is multiply miles by 1.609 and then round to the nearest tenth or hundredth.
13.5 X 1.609 = 21.7215.
Round down to 21.7.
Final Answer: 21.7 Km is equal to 13.5 miles or vice versa.