A spherical hot-air balloon has a diameter has a radius of 27.5 feet when fully inflated. The radius increases at a rate of 1.5 feet per minute. How many minutes will it take to fully inflate the balloon?

The fully inflated balloon’s radius is 27.5 feet, and it grows by 1.5 feet per minute. Starting from a radius of 0, the time is 27.5 ÷ 1.5 ≈ 18.3 minutes, which is closest to 18 minutes. So the answer is B, 18 minutes.

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