Another Geo. Fig. Prob.: The third side of a certain ....

V

vonsmiley

New member
Joined
Jun 22, 2006
Messages
28
So it won't be a shock I don’t know what I’m doing in general, I thought I would put this one out there with the other:

An Isosceles triangle also has two sides with the same length. The third and shortest side of a certain isosceles triangle is one-half the length of each of the equal sides. The perimeter of the triangle is eighty inches. What is the length of each side?

The things I know:
Perimeter is the total of all the sides and that is 80 inches.
Two sides of the triangle are equal and the third one-half that length
the two equal sides are acute so they measure between 0 and 90 degrees

Is there something else I should know? I just don't know.
 
How about the answer?

Use what you have to solve it.

"Two sides of the triangle are equal and the third one-half that length"

L = Length of One of the Equal Sides
L/2 = Length of Shorter Side.

"Perimeter is the total of all the sides and that is 80 inches"

L + L + L/2 = 80

"the two equal sides are acute so they measure between 0 and 90 degrees "

This doesn't make any sense. Sides are not angles. Anyway, it is good that you wrote it. It is good to write down ALL you can think of and worry about actually needing it, later.
 
I see what you mean about "the two equal sides are acute so they measure between 0 and 90 degrees "

the two equal angles are acute but since I'm not looking for that it doesn't matter anyway. Oh, and the answer is 32, 32, 16, but I still can't get past

L + L + L/2 = 80
1L + 1L +L/2 = 80
5/2L=80

Don't laugh. I really am that dumb in math.
:?
 
vonsmiley said:
L + L + L/2 = 80
1L + 1L +L/2 = 80
5/2L=80
Click to expand...
First, fix your notation. (5/2)L and 5/2L and 5/(2L) may not all mean the same thing. Add parentheses to be more clear. It may be fine the way it is, but it never hurts to add clarity.

(5/2)L = 80

Get rid of the fractions by multiplying by 2. (Why did I pick '2'?)

2*(5/2)L = 2*80
5*(2/2)L = 2*80
5*(1)L = 2*80
5L = 2*80
5L = 160

Divide by 5 and you are done. (Why did I pick '5'?)

5L/5 = 160/5
(5/5)L = 160/5
(1)L = 160/5
L = 160/5
L = 32

This is an important moment. Are we done? I'll leave the rest for you.
 
vonsmiley said:
Oh, and the answer is 32, 32, 16, but I still can't get past
L + L + L/2 = 80
I really am that dumb in math: SAY THAT AGAIN AND YOU GET NO HELP!!
Click to expand...
L + L + L/2 = 80
Another way; multiply your equation by 2:
2L + 2L + L = 160
5L = 160

Capish??
 
A bow to the Elite

TK, you are great, and I even feel less dumb. The problem with most math teachers and me is that they don't answer the question "why." You did and showed me I was on the right track. :D The fact that something as simple as the difference in notation could help me see that I could multiple both side to get rid of the fraction. :lol:

Now, that I have L=32
all I have to do is L + L + L/2 or 32 + 32 + 32/2 = 80 to check my answer.

Again, thank you TK!
 
Re: A bow to the Elite

I am still waiting for one tiny thing. You haven't actually answered the question. :shock: Maybe you did on your assignment and you just didn't share it with us. :)

"What is the length of each side?"

It's a triangle. There should be three answers. What are they?
 
Now I'm confused-- as if that's something new :) But the answer is two sides are 32in and one is 16in. and that could be checked by using the perimeter of 80cm.

L + L + L/2 or 32 + 32 + 32/2 = 80in

Did I miss something? :?
 
The only thing you missed is saying this: "...The answer is two sides are 32in and one is 16in." Now you've done it. Good work.
 
You must log in or register to reply here.
Top