There would be four rows of 5. If he added one more row of desks he would have 25 desks.
Each line is a desk
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Answer:
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Step-by-step explanation:
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You're looking for a value

such that

Because the distribution is symmetric, the value of

in either case will be the same.
Now, because the distribution is continuous, you have that

The mean for the standard normal distribution is

, and because the distribution is symmetric about its mean, it follows that

.

You can consult a

score table to find the corresponding score for this probability. It turns out to be

.