Question

....Which lengths could be the sides of a triangle?
A.

17 cm, 5 cm, 13 cm

B.

5 cm, 17 cm, 12 cm

C.

20 cm, 15 cm, 4 cm

D.

15 cm, 20 cm, 3 cm

Answer 1

any angle?

Answer 2

No.

Answer 3

Remember that the sum of any two sides must be greater than the third side.

Answer 4

So which choice meets that requirement?

Answer 5

Triangle has a property that the sum of any two sides of a triangle must be greater than the third side. We'll have to check each option
I'll show you one example, you have to check the others
b)5, 17 12
here 5+12=17 is equal to 17 but we need it to be greater , so these can't be sides of a triangle, Now you check the other options

Answer 6

@ChinaGurl are you trying?

Answer 7

lets allow china to work at their own pace. if they need further clarification, they will ask :) no need to goad them.

Answer 8

This is exactly the same as this:
http://openstudy.com/users/chinagurl#/updates/4f7729a7e4b0ddcbb89da6b1
Please don't ask the same question twice!

Answer 9

Yeah @amistre64
Take your time @ChinaGurl

Answer 10

@chinaGurl --> The deal here is to use the triangle inequality property.
One side of a triangle has to be less than the sum of the other two or no triangle can be formed.

Consider the lengths 1,1,2. Could they be sides of a triangle. No. The 1 and the 1 would collapse on the 2, and form a segment of sorts.

Let's start at Option D and work backwards.
======================

Can 15 cm, 20 cm, 3 cm be sides of a triangle?

You have 3 checks to make. If you get "no" on any one of the three, you can stop, and say "No triangle with these lengths."

Is 15 < 20 + 3 Yes
Is 20 < 15 + 3 NO --> These lengths cannot be sides of a triangle. There is no need to test 3 < 15 + 20.

Option C
=======
20 cm, 15 cm, 4 cm

Three Checks - Take each side and test it against the sum of the other two.

20 < 15 + 4 NO --> These lengths cannot be those of a triangle.

Option B
======
5 cm, 17 cm, 12 cm

Is 5 < 17 + 12 Yes
Is 17 < 5 + 12 No --> These lengths are not those of a triangle

Option A
======
17 cm, 5 cm, 13 cm

Is 17< 5 + 13 Yes
Is 5 < 17 + 13 Yes
Is 13 < 17 + 5 Yes ---> 3 Yes counts means that these lengths could be those of a triangle ------> Answer --> Option A