In the derivation of the formula for volume of a sphere, we started with a cylinder with two cones inside. Imagine passing a horizontal plane through the figure, creating radius b, as shown below.

What is the cross-sectional area of the shaded ring?

πb2 – πr2, or π(b2 – r2)
πb2 + πr2, or π(b2 + r2)
πr2 – πb2, or π(r2 – b2)
πr2 + πb2, or 2π(r2 + b2)

(co 3) the times that customers spend in a book store are normally distributed with a mean of 39.5 minutes and a standard deviation of 9.4 minutes. a random sample of 25 customers has a mean of 36.1 minutes or less. would this outcome be considered unusual, so that the store should reconsider its displays? no, the probability of this outcome at 0.035, would be considered usual, so there is no problem yes, the probability of this outcome at 0.035, would be considered unusual, so the display should be redone no the probability of this outcome at 0.359 would be considered usual, so there is no problem yes, the probability of this outcome at 0.965 would be considered unusual, so the display should be redone