Triangles LMN and STU: LM = ST = 10 cm, MN = TU = 12 cm, LN = SU = 7…

Step by step

The question

Question: which rule shows that triangles LMN and STU are congruent?

1 Match the parts

Congruent means the same shape and the same size.

One fits exactly on top of the other.

The order of the letters shows which corners match: L with S, M with T, N with U.

STU is turned over.

That does not matter.

LM and ST are both 10 cm: a pair of equal sides.

S for side.

MN and TU are both 12 cm: a pair of equal sides.

S for side.

LN and SU are both 7 cm: a pair of equal sides.

S for side.

2 Find the rule

All three pairs are sides.

Side, side, side: S S S.

Three sides fix the triangle.

Like three sticks: they join up in only one way.

So S S S shows the triangles are congruent.

Let's look back.

First: match the parts.

Last: find the rule.