Question

Lucas is planning a trip, using a map with a scale of 1cm to 20 miles. If the destination is 10 cm away on the map, how far away, in miles, is the destination?

Answer 1

200 miles

Explanation:

With these you need to multiply or divide so the units come out right.

You want to end up with miles, and what you know is:

• 1 cm/20 miles
• 10 cm

Do you remember that when you divide by a fraction you get to flip it and multiply? The units would be right if we divided cm by cm/miles:

Centimeters cancel and we're left with 'miles' in the numerator:

• 10 cm is the 10 cm · 20 miles
• 1 cm/20 miles same as: 1 cm

200 miles

You can do it by adding too:

"If 1 cm is 20 miles, then when I go 2 cm on the map that's 40 miles, 5cm is 100 miles, and 10 cm is 200 miles."

Basically for these map questions:

• If they give you the distance on the map, multiply by the scale.
• If they give you the miles, divide by the scale.