ExplanationDraw a bell curve with three standard deviations to the left and the right of mean.

Plug in 50 lbs on the leftmost standard deviation as mentioned in the question. Start with choice (A), plug in 80 lbs for the mean, and solve for the standard deviation. In this case it would be 10, and it’s possible to see that 110 would be the third standard deviation to the right of the mean.

Therefore,

choice (A) satisfies the question. If you repeat this with choice (B), you’ll find that the standard deviation would have to be 11.67. Thus, the value two standard deviations to the right of the mean is 108, and is just shy of what you want.

In

choice (C), the mean is 86, the standard deviation is 12, and 110 will be the second deviation to the right of the mean.

Choice (D) works; the mean is 95, standard deviation is 15, and 120 is the first value to the right of the mean. You can Ballpark to eliminate choice (E). Its standard deviation is about 16, and the first standard deviation to the right would be about 116, which means 110 cannot fall on a standard deviation.

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Sandy

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