Merge pull request #74 from thvardhan/master

add sum of N terms of GP in C

algebra/combinations/c/calculate_combinations.c

@@ -0,0 +1,18 @@
+#include <stdio.h>
+
+
+long long int fact(int n){
+  if(n==1 || n==0)return 1;
+  return fact(n-1)*n;
+}
+
+long long int combination(int n,int r){
+  return fact(n)/(fact(r)*fact(n-r));
+}
+
+void main(){
+	int n,r;
+	printf("Enter N then R from nCr\n");
+	scanf("%d%d",&n,&r);
+	printf("Value of %dC%d is %ld",n,r,combination(n,r));
+}

algebra/sum_of_n_terms_of_gp/c/sumOfGP.c

@@ -0,0 +1,11 @@
+#include<stdio.h>
+#include<math.h>
+
+void main(){
+  float n,r,a,sum;
+  printf("Enter the first term of the GP then Common Ratio then number of terms.\n");
+  scanf("%f%f%f",&a,&r,&n);
+  sum=(a*(1-pow(r,n)))/(1-r);
+  printf("The sum of first %.0f terms is %f\n",n,sum);
+}
+