Can 1, 2 and 5 make a triangle

Step by step

The question

Question: can sides of 1, 2 and 5 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 5.

We lay it down first.

The two short sides are 1 and 2.

Together: 3.

2 Compare with the longest

Swing them up from the ends.

3 is less than 5: they do not even reach each other.

Careful!

Adding the long side to a short one is always enough.

The test is the two short sides.

So no: they cannot make a triangle.

3 Check

Let's check the other two pairs: 1 plus 5 is 6, and 2 plus 5 is 7.

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.