diff --git a/2nd_sem/Pull_Requests/Riya_Singh_DS_38/Problem1.c b/2nd_sem/Pull_Requests/Riya_Singh_DS_38/Problem1.c
new file mode 100644
index 0000000..60fe8cb
--- /dev/null
+++ b/2nd_sem/Pull_Requests/Riya_Singh_DS_38/Problem1.c
@@ -0,0 +1,22 @@
+#include<stdio.h>
+
+int main()
+{
+    int n = 3 ;
+    
+    printf("Enter number : ");
+    scanf("%d",&n);
+
+    printf("%d ",n);
+
+     while(n != 1){
+        if(n % 2 == 0){
+            n = n/2;
+        }
+        else{
+            n=3*n+1;
+        }
+        printf("%d ",n);
+    }
+    return 0;
+}
diff --git a/2nd_sem/Pull_Requests/Riya_Singh_DS_38/problem2.c b/2nd_sem/Pull_Requests/Riya_Singh_DS_38/problem2.c
new file mode 100644
index 0000000..60fe8cb
--- /dev/null
+++ b/2nd_sem/Pull_Requests/Riya_Singh_DS_38/problem2.c
@@ -0,0 +1,22 @@
+#include<stdio.h>
+
+int main()
+{
+    int n = 3 ;
+    
+    printf("Enter number : ");
+    scanf("%d",&n);
+
+    printf("%d ",n);
+
+     while(n != 1){
+        if(n % 2 == 0){
+            n = n/2;
+        }
+        else{
+            n=3*n+1;
+        }
+        printf("%d ",n);
+    }
+    return 0;
+}
diff --git a/2nd_sem/Pull_Requests/Riya_Singh_DS_38/problem3.c b/2nd_sem/Pull_Requests/Riya_Singh_DS_38/problem3.c
new file mode 100644
index 0000000..b5e0fd0
--- /dev/null
+++ b/2nd_sem/Pull_Requests/Riya_Singh_DS_38/problem3.c
@@ -0,0 +1,35 @@
+#include <stdio.h>
+
+int main() 
+{
+    int n, t1, t2, x, y, movie = 1, endt;
+    
+
+    printf("Enter the number of movies : ");
+    scanf("%d", &n);
+    
+    printf("Enter the starting time of the 1st movie : ");
+    scanf("%d", &t1);
+    
+    printf("Enter the ending time of the 1st movie : ");
+    scanf("%d", &t2);
+    endt=t2;
+
+    for (int i = 1; i < n; i++) {
+       
+        printf("Enter starting time of the next movie : ");
+        scanf("%d",&x);
+
+        printf("Enter the endig time of the next movie : ");
+        scanf("%d",&y);
+        
+        if (endt<=x) {
+            movie++;
+            endt = y;
+        }
+    }
+
+    printf("Maximum number of movies that can be watched are : %d\n", movie);
+
+    return 0;
+}