IOQM 2022 Part 3 #ioqm2022

IOQM 2022 Part 3 #ioqm2022

IOQM 2022 Questions 18 to 22 𝐿𝑒𝑑 π‘š, 𝑛 𝑏𝑒 π‘›π‘Žπ‘‘π‘’π‘Ÿπ‘Žπ‘™ π‘›π‘’π‘šπ‘π‘’π‘Ÿπ‘  π‘ π‘’π‘β„Ž π‘‘β„Žπ‘Žπ‘‘ π‘š + 3𝑛 – 5 =2𝐿𝐢𝑀(π‘š, 𝑛) – 11𝐺𝐢𝐷(π‘š, 𝑛). 𝐹𝑖𝑛𝑑 π‘‘β„Žπ‘’ π‘šπ‘Žπ‘₯π‘–π‘šπ‘’π‘š π‘π‘œπ‘ π‘ π‘–π‘π‘™π‘’ π‘£π‘Žπ‘™π‘’π‘’ π‘œπ‘“ π‘š + 𝑛. Consider a string of n 1’s. We wish to place some + signs in between so that the sum is 1000. For instance, if n = 190, one may put + signs so as to get 11 ninety times and 1 ten times and get the sum 1000. If a is the number of positive integers n for which it is possible to place + signs so as to get the sum 1000, then find the sum of the digits of a. πΉπ‘œπ‘Ÿ π‘Žπ‘› π‘–π‘›π‘‘π‘’π‘”π‘’π‘Ÿ 𝑛β‰₯ 3 π‘Žπ‘›π‘‘ π‘Ž π‘π‘’π‘Ÿπ‘šπ‘’π‘‘π‘Žπ‘‘π‘–π‘œπ‘› 𝐾 = (𝑝1, 𝑝2, …, 𝑝𝑛)π‘œπ‘“ {1, 2, …, 𝑛}, 𝑀𝑒 π‘ π‘Žπ‘¦ 𝑝1 𝑖𝑠 π‘Ž π‘™π‘Žπ‘›π‘‘π‘šπ‘Žπ‘Ÿπ‘˜ π‘π‘œπ‘–π‘›π‘‘ 𝑖𝑓 2 less than 𝑙 less than 𝑛 – 1 π‘Žπ‘›π‘‘ (𝑝𝑙 –1 – 𝑝𝑙)(𝑝𝑙 + 1 – 𝑝𝑙) greater than 0. πΉπ‘œπ‘Ÿ 𝑒π‘₯π‘Žπ‘šπ‘π‘™π‘’, π‘“π‘œπ‘Ÿ 𝑛 = 7, π‘‘β„Žπ‘’ π‘π‘’π‘Ÿπ‘šπ‘’π‘‘π‘Žπ‘‘π‘–π‘œπ‘› (2, 7, 6, 4, 5, 1, 3)β„Žπ‘Žπ‘  π‘“π‘œπ‘’π‘Ÿ π‘™π‘Žπ‘›π‘‘π‘šπ‘Žπ‘Ÿπ‘˜ π‘π‘œπ‘–π‘›π‘‘π‘ : 𝑝2 = 7, 𝑝4 = 4, 𝑝5 = 5 π‘Žπ‘›π‘‘ 𝑝6 = 1. πΉπ‘œπ‘Ÿ π‘Ž 𝑔𝑖𝑣𝑒𝑛 𝑛β‰₯ 3, 𝑙𝑒𝑑 𝐿(𝑛)π‘‘π‘’π‘›π‘œπ‘‘π‘’ π‘‘β„Žπ‘’ π‘›π‘’π‘šπ‘π‘’π‘Ÿ π‘œπ‘“ π‘π‘’π‘Ÿπ‘šπ‘’π‘‘π‘Žπ‘‘π‘–π‘œπ‘› π‘œπ‘“ {1, 2, …, 𝑛}π‘€π‘–π‘‘β„Ž 𝑒π‘₯π‘Žπ‘π‘‘π‘™π‘¦ π‘œπ‘›π‘™π‘¦ π‘œπ‘›π‘’ π‘™π‘Žπ‘›π‘‘π‘šπ‘Žπ‘Ÿπ‘˜ π‘π‘œπ‘–π‘›π‘‘. 𝐹𝑖𝑛𝑑 π‘‘β„Žπ‘’ π‘šπ‘Žπ‘₯π‘–π‘šπ‘’π‘š 𝑛 greater than 3 π‘“π‘œπ‘Ÿ π‘€β„Žπ‘–π‘β„Ž 𝐿(𝑛) 𝑖𝑠 π‘Ž π‘π‘’π‘Ÿπ‘“π‘’π‘π‘‘ π‘ π‘žπ‘’π‘Žπ‘Ÿπ‘’. An ant is at a vertex of a cube. Every 10 minutes it moves to an adjacent vertex along an edge. If N is the number of one hour journeys that end at the starting vertex, find the sum of the squares of the digits of N π΅π‘–π‘›π‘Žπ‘Ÿπ‘¦ π‘ π‘’π‘žπ‘’π‘’π‘›π‘π‘’ 𝑖𝑠 π‘Ž π‘ π‘’π‘žπ‘’π‘’π‘›π‘π‘’ 𝑖𝑛 π‘€β„Žπ‘–π‘β„Ž π‘’π‘Žπ‘β„Ž π‘‘π‘’π‘Ÿπ‘š 𝑖𝑠 π‘’π‘žπ‘’π‘Žπ‘™ π‘‘π‘œ 0 π‘œπ‘Ÿ 1. 𝐴 π‘π‘–π‘›π‘Žπ‘Ÿπ‘¦ π‘ π‘’π‘žπ‘’π‘’π‘›π‘π‘’ 𝑖𝑠 π‘π‘Žπ‘™π‘™π‘’π‘‘ π‘“π‘Ÿπ‘–π‘’π‘›π‘‘π‘™π‘¦ 𝑖𝑓 π‘’π‘Žπ‘β„Ž π‘‘π‘’π‘Ÿπ‘š 𝑖𝑠 π‘Žπ‘‘π‘—π‘Žπ‘π‘’π‘›π‘‘ π‘‘π‘œ π‘Žπ‘‘ π‘™π‘’π‘Žπ‘ π‘‘ π‘œπ‘›π‘’ π‘‘π‘’π‘Ÿπ‘š π‘‘β„Žπ‘Žπ‘‘ 𝑖𝑠 π‘’π‘žπ‘’π‘Žπ‘™ π‘‘π‘œ 1. πΉπ‘œπ‘Ÿ 𝑒π‘₯π‘Žπ‘šπ‘π‘™π‘’, π‘‘β„Žπ‘’ π‘ π‘’π‘žπ‘’π‘’π‘›π‘π‘’ 0, 1, 1, 0, 0, 1, 1, 1 𝑖𝑠 π‘“π‘Ÿπ‘–π‘’π‘›π‘‘π‘™π‘¦. 𝐿𝑒𝑑 𝐹(𝑛) π‘‘π‘’π‘›π‘œπ‘‘π‘’ π‘‘β„Žπ‘’ π‘›π‘’π‘šπ‘π‘’π‘Ÿ π‘œπ‘“ π‘“π‘Ÿπ‘–π‘’π‘›π‘‘π‘™π‘¦ π‘π‘–π‘›π‘Žπ‘Ÿπ‘¦ π‘ π‘’π‘žπ‘’π‘’π‘›π‘π‘’π‘  π‘€π‘–π‘‘β„Ž 𝑛 π‘‘π‘’π‘Ÿπ‘šπ‘ . 𝐹𝑖𝑛𝑑 π‘‘β„Žπ‘’ π‘ π‘šπ‘Žπ‘™π‘™π‘’π‘ π‘‘ π‘π‘œπ‘ π‘–π‘‘π‘–π‘£π‘’ π‘–π‘›π‘‘π‘’π‘”π‘’π‘Ÿ 𝑛 greater than or equal to 2 π‘ π‘’π‘β„Ž π‘‘β„Žπ‘Žπ‘‘ 𝐹(𝑛) greater than100.