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