diff --git a/compound_random_variable/Makefile b/compound_random_variable/Makefile
new file mode 100644
index 0000000..8de5e43
--- /dev/null
+++ b/compound_random_variable/Makefile
@@ -0,0 +1,27 @@
+example3_8:=example3_8.out
+OBJS:=../utils/parse_arg.o ../utils/rand_gen.o
+OBJS_3_8:=example3_8.o
+OBJDIR:=output image
+CXX=g++
+CXXFLAGS:=-std=c++14
+
+.DEFAULT_GOAL:=all
+
+astyle:
+	astyle --style=google --indent=spaces=2 *.cc
+
+all: $(OBJDIR) example3_8
+
+run: all
+
+example3_8: $(OBJS_3_8) $(OBJS)
+	$(CXX) $(CXXFLAGS) $^ -o $(example3_8)
+
+%.o: %.c %.h
+	$(CXX) $(CXXFLAGS) -c $^
+
+$(OBJDIR):
+	mkdir -p $@
+
+clean:
+	rm *.o $(OBJS)
\ No newline at end of file
diff --git a/compound_random_variable/example3_8.cc b/compound_random_variable/example3_8.cc
new file mode 100644
index 0000000..95fe22e
--- /dev/null
+++ b/compound_random_variable/example3_8.cc
@@ -0,0 +1,36 @@
+#include <cstdio>
+#include "../utils/rand_gen.h"
+#include <map>
+
+int main(int argc,char *argv[]){
+    // random number generator
+    rand_gen *gen = new rand_gen();
+
+    // upperbound: t = X1+X2
+    double t=10000,counter=0.0,mu1=1,mu2=2;
+    // X1, X2
+    std::map<double,int> X1,X2;
+
+    while(t--){
+        // double ts = gen->exponential(mu1);
+        X1[(int)gen->exponential(mu1)]++;
+        X2[(int)gen->exponential(mu2)]++;
+    }
+
+    double sum_X1=0.0,sum_X2=0.0;
+    for(auto&it: X1){
+        sum_X1+=it.second;
+    }
+    for(auto&it: X2){
+        sum_X2+=it.second;
+    }
+
+    for(auto&it:X1){
+        printf("[ %lf ]: %lf\n",it.first,it.second/sum_X1);
+    }
+    /*for(auto&it:X2){
+        printf("[ %lf ]: %lf\n",it.first,it.second/sum_X2);
+    }*/
+
+    return 0;
+}
\ No newline at end of file