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I have no idea how to help my son solve this problem

The letter F stands for the date that Amelia Earhart was born. Use the clues to figure out F.

1) The difference between the two digits of F is not 3.

2) F x F >= 400

3) 2 is a factor of F.

4) 3 is a factor of F.

5) 2 x F <= 60

For FxF to be at least 400, that makes F at least 20.

By (3), if 2 is a factor of F, then F is 20, 22, 24, 26, 28, or 30.

By (4), if 3 is a factor of F, the only two numbers of the last set divisible by 3 are 24 and 30.

By (5), for both cases, 2F is <= 60, for when F is 24 or F is 30, 2F is 48 or 60.

By (1), the difference between the digits for 24 is 4-2=2 and for 30 it is 3-0=3

so the 2nd choice of 30 is eliminated.

That would make the answer 24.

Just for fun, 24 is also 4 factorial (that is, 24=1*2*3*4).

Algebra

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