每日一题——第四十七题

题目：计算1* 2 + 2 * 3 + … + 20 * 21

#include<stdio.h>/// <summary>
/// 计算一个数num * （num - 1）
/// </summary>
/// <param name="num"></param>
/// <returns></returns>
int Calculate_Multiplication(int num) {return num * (num - 1);
}int main() {int sum = 0;for (int i = 2; i <= 21; i++) {sum += Calculate_Multiplication(i);}printf("1*2 + 2*3 + ... + 20*21 = %d", sum);
}