A triangle has side lengths measuring 20 cm, 5 cm, and n cm. Which describes the possible values of n?

For three lengths to form a triangle, the third side must be greater than the difference of the other two sides and less than their sum. Here, 20 − 5 = 15 and 20 + 5 = 25, so n must satisfy 15 < n < 25. This is choice D, “15 < n < 25.”

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