There are four types of triangle:
(A mark on a line means that it is the same length as another line with the same mark).
In a triangle, one angle is 30º and a second angle is 60º.
What type of triangle is it?
The two angles add up to 90º.
There are 180º in a triangle, so the remaining angle is 90º.
Answer: Right angled triangle
A triangle has sides of length `x`, `x` and `2x`.
What type of triangle is it?
Two of the sides are the same length.
Answer: Isosceles triangle.