设n=666.66*9*7777.7,(注:有n个6,n个7),则n的各位数字之和是多少?
问题描述:
设n=666.66*9*7777.7,(注:有n个6,n个7),则n的各位数字之和是多少?
答
66*77*9 = 45738;
666*777*9 = 4657338;
6666*7777*9 = 466573338;
66666*77777*9 = 46665733338;
各位之和 = 4 + 5 + 7 + 8 + 6(n - 2) + 3(n - 1)
= 9(n + 1)