Posted by lisa on .
an isosceles triangle has a perimeter of in. the congruent sides measure (2x+9)cm. The length of the third side is 3 x cm. what is the value of x?

geometry  incomplete 
Ms. Sue,
What is the perimeter?

geometry 
lisa,
an isosceles triangle has a perimeter of 60 in. the congruent sides measure (2x+9)cm. The length of the third side is 3x cm. what is the value of x?
Again...sorry. = ) 
geometry 
Ms. Sue,
How do you think you should solve this problem?

geometry 
lisa,
I really have no idea. I am more confused with every question.

geometry 
Ms. Sue,
Are you sure that the perimeter is 60 inches?
2(2x + 9) + 3x = 60
Solve for x. 
geometry 
Ms. Sue,
If the perimeter is 90 inches, forget the solution I posted above.

geometry 
lisa,
19.2 cm?

geometry 
lisa,
x = 19.2cm? (the perimeterr is 60 in.)

geometry 
Ms. Sue,
Substitute 19.2 for x and see if it works.

geometry 
lisa,
It does...right? Oh Lord...

geometry 
Ms. Sue,
I'll bet the perimeter is 60 cm.
2(2x + 9) + 3x = 60
2(38.4 + 9) + 3(19.2) = 60
94.8 + 57.6 does not equal 60
Work this equation.
2(2x + 9) + 3x = 60
You should find that x is a whole number between 5 and 10. 
geometry 
lisa,
how about x=6...that works.

geometry 
Ms. Sue,
Yay! You got it!

geometry 
lisa,
really..cuz that answer I didn't convert cm to inches. when I do I get x = 18.86 now. Please confirm. my brain hurts.

geometry 
Ms. Sue,
Are you absolutely sure that the perimeter was given in inches, not centimeters?
If you are  then I'm off base because I've figured the perimeter as 60 centimeters. 
geometry 
lisa,
no, the perimeter is 60 inches. ha..hence the confusion.
1 in = 2.54 cm
60 in =152.4cm
7x=152.418
7x=134.4 / 7
x=19.2cm
Whadda ya think? 
geometry 
Ms. Sue,
Ahh! It looks like you're right.