Suppose a chord in a circle is 80 centimeters long and it is 30cm from the center of the circle. How could I find the measurements of a radius of the circle.

Draw a line from the center of the circle to the middle of the chord. It has length 30 cm

Now, draw a line from the center of the circle to the end of the chord. You now have a right triangle. See it?

It has hypoteneuse length, which is the radius, of \sqrt{40^{2}+30^{2}}

I don't understand what happened to chors that is 80cm long.

Ok Ok so I have to add 30 +40-180=110
Because the answers are a. 30cm
b. 50cm
c. 80cm
d. 110cm

What are you doing with 30+40-180? I more or less gave you the solution.

Besides, 30+40-180=-110.

The initial question is kind of vague... it doesn't say what part of the chord is 30 cm from the center and it doesn't say if the chord is touching any of the radius. Not enough info for a true solution.

I got it the answer is 50cm.
R=(30) square + (40) square
R= square root (2500)
=50


Thank you

There's enough information if you are willing to fore go pedantry.