posted by jake .
Circle O above has a circumference of 240 cm and arc XW has a length of 60 cm. What is the measure of the central angle associated with arc XW?
first we get the ratio of the arclength to circumference:
60 cm / 240 cm = 1/4
since the arc covers 1/4 of the circumference, it also means that it forms 1/4 of the total angle of a circle.
angle of a circle is 360 degrees, thus central angle associated by XW is:
(1/4)*360 = 90 degrees
hope this helps~ :)