How many natural number lie strictly between 8^2 to 9^2?

Answer: B. 16

8^2 = 64 and 9^2 = 81. Strictly between them means 65 to 80, which is 80 - 65 + 1 = 16 numbers. In general there are 2n numbers between n^2 and (n + 1)^2.

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