The answer contains 3 digits, 4 9 and B.

From the problem, it is clear that the value of B should be greater than 4 and less than 9.

If the value of B is less than 4, the answer will contain only two digits instead of 3.

If the value of B is greater than 9, the solution will contain more than 3 digits.

Since the units place contains 1, and B ranges anywhere between 4 and 9, The tenth place when multiplied by B gives 49.

⇒ BxB = 49.

⇒ B = 7.