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Can 3, 4, 8 make a triangle

Step by step, with the reason for every step · Can it make a triangle · Geometry

Step by step

The question

Question: can sides of 3, 4 and 8 make a triangle?

sides 3, 4, 8

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

Else they cannot meet.

the two short sides must reach
round the longest one

1 Add the two short sides

The longest side is 8.

We lay it down first.

The two short sides are 3 and 4.

Together: 7.

= 3 + 4 = 7

2 Compare with the longest

Swing them up from the ends.

7 is less than 8: 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.

Careful: add the two SHORT sides

So no: they cannot make a triangle.

= 7 < 8 → no triangle

3 Check

Let's check the other two pairs: 3 plus 8 is 11, and 4 plus 8 is 12.

Both are more than the third side.

So only the short pair decides.

So the answer is right!

3 + 8 = 11 > 4, 4 + 8 = 12 > 3

Let's look back.

First: add the two short sides.

Then: compare with the longest.

Last: check.

Answer
= 7 < 8 → no triangle

Your turn

Try this one yourself, then check:

sides 9, 9, 19
Show the answer
no

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