Calculating simple mathematical formulas in C language

Find the sum of the first 5 items of SN=A+AA+AAA+AAAA+AAAAA, where a is a number

such as 2+22+222+2222+22222

#include <stdio.h>

int main ()

{

int num=0;

int n=0;

int sum=0;

int tmp=0;

scanf ("%d", &num);

scanf ("%d", &n);

Tmp=num;

while (n)

{

sum+=tmp;

Tmp=tmp*10+num;

n--;

}

printf ("%d\n", sum);

System ("pause");

return 0;

}

The results of the program run are as follows:

650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M02/74/C6/wKiom1Yon5jgbtuRAACuksyEFCA693.jpg "title=" The sum of the first 5 items. png "alt=" wkiom1yon5jgbturaacuksyefca693.jpg "/>

9 times between 1~100. #include <stdio.h>int main () {int i=0;int count=0;for (i=1;i<100;i++) {if (i%10==9) count++; if (i/10==9) count++;} printf ("%d\n", count); System ("pause"); return 0;}

The result of the program operation is:

650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M00/74/C5/wKiom1Yon3azkZGlAADIplTkNZk266.jpg "title=" 9 times. png "alt=" wkiom1yon3azkzglaadipltknzk266.jpg "/>

Calculating simple mathematical formulas in C language