Question

The circumference of a roll of party streamers is 9 inches. The circumference decreases by 2 inches after you use the streamers to decorate for a graduation party. Find the diameter of the roll after the decrease. Round your answer to the nearest hundredth.

Answer 1

For that case the new circumference is:
 C = 9 - 2
 C = 7 inches
 By definition, the circumference is:
 C = 2 * pi * r
 Where,
 r: radio
 Substituting values:
 7 = 2 * pi * r
 Clearing the radio:
 r = 7 / (2 * pi)
 Then, the diameter is:
 d = 2 * r
 Substituting:
 d = 2 * (7 / (2 * pi))
 d = 2.228169203
 Round to the hundredth:
 d = 2.23 inches
 Answer:
 The diameter of the roll after the decrease is:
 d = 2.23 inches