Question

If j, k, and n are consecutive integers such that 0 less than j less than k less than n and the units (ones) digit of the product j times n is 9, what is the units digit of k?

Answer 1

HINT:

Since j, k and n are consecutive integers, express them all in terms of k, i.e. you have:\[k-1,k,k+1\]you should then be able to reason about the units digit of k from the information given to you