Brandon is reading a book Flatland and notices that the product of the numbers of the two pages his book is open to has a units digit of 6. What is the units digits of the sum of the two pages numbers?

Answer 1

since the page numbers must be consecutive,
the two pages can only end in 2 and 3

e.g. 52 and 53 ---> 2 x 3 = 6

so the sum must end in 5

e.g. 52+53 = 105