MathDB
2018 Theme #4

Source:

November 13, 2018

Problem Statement

I have two cents and Bill has nn cents. Bill wants to buy some pencils, which come in two different packages. One package of pencils costs 6 cents for 7 pencils, and the other package of pencils costs a dime for a dozen pencils (i.e. 10 cents for 12 pencils). Bill notes that he can spend all nn of his cents on some combination of pencil packages to get PP pencils. However, if I give my two cents to Bill, he then notes that he can instead spend all n+2n+2 of his cents on some combination of pencil packages to get fewer than PP pencils. What is the smallest value of nn for which this is possible?
Note: Both times Bill must spend all of his cents on pencil packages, i.e. have zero cents after either purchase.