DAY 36

Comment

The missing number will be one of these:
49, 51, 53, 55, 57.
Butit is not 49, because 7 x 7 = 49.
What about the others?

Answer

53.

Readers' methods

Clare H, Toulouse 31700:
It is not 51 because 51 is in the 3, 17, 1 & 51 times table.
It is 53 because 53 is in the 53 times table and 1 times table and it's in no other times table.

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