Can 8, 15 and 7 make a triangle

Step by step

The question

Question: can sides of 8, 15 and 7 make a triangle?

For a triangle, the two short sides together must be longer than the longest side.

Else they cannot meet.

1 Add the two short sides

The longest side is 15.

We lay it down first.

The two short sides are 7 and 8.

Together: 15.

2 Compare with the longest

Swing them up from the ends.

15 is exactly 15: they only meet lying flat on the long side.

Careful!

7 plus 8 is exactly 15.

The sides lie flat on top of each other.

That is a line, not a triangle.

So no: they cannot make a triangle.

3 Check

Let's check the other two pairs: 7 plus 15 is 22, and 8 plus 15 is 23.

Both are more than the third side.

So only the short pair decides.

So the answer is right!

Let's look back.

First: add the two short sides.

Then: compare with the longest.

Last: check.