Question 772746
The worst guess is 12 away.  The number of pennies has to be between the lowest guess, 42, and the highest guess, 65.  If it were higher than 65 or lower than 42, then the 2nd worst guess could not be 11 away.  That means the number is either 42+12 = 54 or 65-12 = 53.  It cannot be 54, since there are no guesses that are 2 away and 54 and 52 are two apart.  So the answer is 53.
Check:
65 - 53 = 12
53 - 42 = 11
62 - 53 = 9
59 - 53 = 6
53 - 49 = 4
53 - 52 = 1