Answer: D. 55 minutes
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Explanation:
If the radius is r = 7, then the volume of the sphere is approximately...
V = (4/3)*pi*r^3
V = (4/3)*3.14*7^3
V = 1436.02667 cubic feet approximately
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The air is escaping at a rate of 26 cubic feet per minute. After x minutes, the balloon loses 26x cubic feet of air.
If we start with roughly 1436.02667 cubic feet of air, and lose 26x cubic feet of air after x minutes, then we have 1436.02667-26x cubic feet of air leftover. Set this equal to 0 to find out when the balloon will run out of air.
1436.02667-26x = 0
1436.02667 = 26x
26x = 1436.02667
x = 1436.02667/26
x = 55.231795
Rounded to the nearest minute, we get roughly 55 minutes.
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Side note: to get a more accurate answer, you'll need to use a more accurate version of pi.
