MathDB
mercant and customer debts, located along a ring road

Source: Tuymaada 1995 p4

April 27, 2019
combinatoricscircleSum

Problem Statement

It is known that the merchant’s nn clients live in locations laid along the ring road. Of these, kk customers have debts to the merchant for a1,a2,...,aka_1,a_2,...,a_k rubles, and the merchant owes the remaining nkn-k clients, whose debts are b1,b2,...,bnkb_1,b_2,...,b_{n-k} rubles, moreover, a1+a2+...+ak=b1+b2+...+bnka_1+a_2+...+a_k=b_1+b_2+...+b_{n-k}. Prove that a merchant who has no money can pay all his debts and have paid all the customer debts, by starting a customer walk along the road from one of points and not missing any of their customers.