britbrat4601 3 years ago Which three lengths could be the lengths of the sides of a triangle? A. 12 cm, 5 cm, 17 cm B. 10 cm, 15 cm, 24 cm C. 9 cm, 22 cm, 11 cm D. 21 cm, 7 cm, 6 cm

1. geoffb

Remember that the sum of the two shorter legs have to be greater than the longest leg. If they sum to less, they can't even touch. If they sum to the same, they are on the same line as the long leg, and it is not a triangle.

2. britbrat4601

so b?

3. geoffb

Yes.

4. britbrat4601

5. geoffb

A would just be a line, and C and D could not connect to form a triangle.

6. geoffb

No problem. :)

7. vitorfleite

Everyone can be a triangle, scalene triangles.

8. geoffb

@vitorfleite No they can't. Draw them out on a piece of paper and you'll see.

9. vitorfleite

I draw a triangle with the lenghts of C, now.

10. geoffb

|dw:1353900288402:dw| You can't make the 12 and 5 cm lines into a triangle. The only way they can connect is as a straight line.

11. geoffb

|dw:1353900366005:dw| The two shorter lines cannot connect.

12. geoffb

In C and D, the shorter lines don't even add up to the big line. It's not mathematically possible for two short lines to create a triangle with a long line unless the two short lines sum to greater than the long line.

13. vitorfleite

I understood now, I did wronggg.

14. geoffb

No worries. I made the exact same false assumption on here a few months ago. :)