Find the actual length of a wall on a map with scale 1:25000

[tehmatriks]

Homework Statement

The scale on a map is 1:25000. The length of a wall on the map is 3.2 mm. Find the actual length in metres.

Homework Equations

The Attempt at a Solution

 

[Mark44]

EDIT: Fixed momentary lapse of brain.
Each 1 mm distance on the map represents 25,000 mm (= 25 meters) on the ground. If the length of some feature on the map happened to be 10 mm, you would set up a proportion like this, where x represents the actual length of the feature, in mm.

$$\frac{1}{25000}=\frac{10}{x}$$

After solving for x in this equation, convert to meters.

 

[tehmatriks]

Each 1 mm distance on the map represents 25,000 mm (= 2.5 meters) on the ground. If the length of some feature on the map happened to be 10 mm, you would set up a proportion like this, where x represents the actual length of the feature, in mm.

$$\frac{1}{25000}=\frac{10}{x}$$

After solving for x in this equation, convert to meters.

25,000 x 3.2 = 80,000 x 10^-3 = 80 cm

 

[Mentallic]

25,000 mm (= 2.5 meters)

Either a typo or a brain fart, 25m

25,000 x 3.2 = 80,000 x 10^-3 = 80 cm

It shouldn't be cm.
25,000 x 3.2 mm = 80,000 mm = 80,000 x 10^-3 m = 80 m

 

[tehmatriks]

yea, that was a typo

thanks fellas, I've just gotten to this chapter and the examples always leave out the good stuff, so many thanks.

 

[Mark44]

Either a typo or a brain fart, 25m

Unfortunately, the latter. It looked odd to me, but I still didn't catch it.

It shouldn't be cm.
25,000 x 3.2 mm = 80,000 mm = 80,000 x 10^-3 m = 80 m