scale drawings

[kcole09]

I am working on scale drawings and cannot seem to get it, your help would be greatly appreciated. here goes
a map has a scale of 1 inch: 3 kilometers. Use the given actual distance to find the distance on the map.

1.5 km

 

[Loren]

Are you in the topic "ratio and proportion"?

Here's one approach. 1 inch on the map represents 3 km in the real world.

You can use the ratio inches/km. It could be $\displaystyle \frac{1.in.on.map}{3.km.real}$. ("." represent spaces)

Now, using that ratio, build a proportion in which that ratio appears on one side of the equal sign and the ratio stating the relationship of the number of inches on the map that you would call "x" and the number of given kms is on the other side of the equal sign.

You should end up with $\displaystyle \frac{1}{3}=\frac{x}{1.5}$. It is important that if the inches are in the numerator on the left, then inches are in the numerator on the right. The kms must be in the denominator on both sides.