Math Puzzle Answer

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Upside Down Calculator - Answer

The original number displayed was 9,126. Suzie saw 9,216 when it was turned upside down, or the square of 96.

When Glen multiplied the number by 2 he got 18,252, Suzie saw it as 25,281 when she turned it upside down - the square of 159.

The digits 0, 1, 2, 5, 6, 8, and 9 are all digits when they are looked at upside down. All of them appear as the same number except 6 and 9 which are reversed.

Make a list of all the squares that don't contain a 3, 4 or 7 or end in 0. Convert them to their upside down values, double them and discard those that contain a 3, 4, or 7. Convert those remaining to their upside down values and take the square root of each. The number 9,216 is the only integer which works and fits on a seven digit calculator.