How_To_Be_Good_At_Math

What is a line? 4 Geometry

What is a line?

A line joins two points together. In geometry, lines can

be either straight or curved. A line has a length that

you can measure, but it has no thickness.

A B

Prove it!

This map shows three possible

routes between points A and B.

Here is an easy way to prove that

the straight line between the

two is the shortest route.

The curved line bends

round the trees, making

the line between A and B

longer than the straight line.

Look at the straight line

between A and B. It shows

us the shortest distance

between the two points.

Route 1 is a straight path. Stretch

a piece of string from Point A to

Point B along the path. Make a mark

on the string where it reaches Point B.

Now do the same for Route 2,

and mark where the string

reaches Point B. The new mark is

further along the string, so Route 2

must be longer than Route 1.

Now put the string along Route 3,

the river. The mark you make this

time will be the furthest along the

string. So, Route 3 is the longest route.

Route 1

Route 2

Route 3

A B

A

B

We call lines

one-dimensional.

They have length but

no thickness.

204_205_What_is_a_Line.indd 204 29/02/2016 18:04