Question

A map has a key showing that every 3 centimeters = 5 kilometers. How far apart are

two cities if the map shows they are 81 centimeters apart?

Answer 1

135 km

Explanation:

5 km / 3cm * 81 cm = 135 km

( see how the 'cm' cancel and you are left with 'km' as your answer?)

Answer 2

Let's consider the information given to us:

• 3 centimeters = 5 kilometers ⇒
  `(3 cm)/(5 km)`
• 81 centimeters = x kilometers ⇒
  `(81 cm)/(x km)`

Now we know these proportions are equal, so:

`(3)/(5)=(81)/(x)\\ 3x = 5 * 81\\3x = 405\\x = 135`

Thus the two cities are 135 km apart

Answer: 135 km

Hope that helps!