#include<bits/stdc++.h>
using namespace std;
int main(){
	int N,sm = 0,a;
	cin >> N;
	for (int i = 1;i <= N;i++){
		cin >> a;
		sm+=a;//往sm中"塞进"a的值
	} 
	double sum = sm * 1.0;//转化成double
	printf("%.2lf",sum / N);//保留小数点后2位

	return 0;
}

可以直接把累加器定义成double,但小数有误差,尽量用整数的形式去存

#include <bits/stdc++.h>

using namespace std;

int main(){

int n,age[101];

double avrrage,sum=0;

int i;

cin>>n;

for(i=1;i<=n;i++){

	cin>>age[i];

	sum+=age[i];

}

avrrage=sum/n;

printf("%.2lf\n",avrrage);

return 0;

}

#include using namespace std; int main() { int n; cin >> n; double sum = 0;//累加器设double变量 for (int i = 1; i <= n; i ++) { int x; cin >> x; sum += x;//累加答案 } printf ("%.2lf", sum/n);//保留两位小数 return 0; }