Question 1187439
Ren inflates a spherical balloon to a circumference of about 14 inches. He then adds more air to the until the circumference is 18 inches. What volume of air was added to the balloon? 
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C = 2pi*r
14 = 2pi*r --> r = 7/pi
18 = 2pi*r --> r = 9/pi
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Vol = 4pi*r^3/3
Diff = 4pi/3*((9/pi)^3 - (7/pi)^3)
= 4pi*(386/pi^3)
= 1544/pi^2 = ~156.44 cubic inches (assuming constant temp and pressure) but adding air does increase the pressure.
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"about 14 inches" makes it less accurate.
Not a well posed problem.