diff --git a/rust/interpreter/src/lib.rs b/rust/interpreter/src/lib.rs
index b8ecdeb..2170ac2 100644
--- a/rust/interpreter/src/lib.rs
+++ b/rust/interpreter/src/lib.rs
@@ -560,6 +560,24 @@ impl<'a> Interpreter<'a> {
                             Err(anyhow!("Type mismatch for fn:minus"))
                         }
                     }
+                    "fn:mult" => {
+                        if let (Value::Number(a), Value::Number(b)) = (&vals[0], &vals[1]) {
+                            Ok(Value::Number(a * b))
+                        } else {
+                            Err(anyhow!("Type mismatch for fn:mult"))
+                        }
+                    }
+                    "fn:div" => {
+                        if let (Value::Number(a), Value::Number(b)) = (&vals[0], &vals[1]) {
+                            if *b == 0 {
+                                Err(anyhow!("Division by zero"))
+                            } else {
+                                Ok(Value::Number(a / b))
+                            }
+                        } else {
+                            Err(anyhow!("Type mismatch for fn:div"))
+                        }
+                    }
                     _ => Err(anyhow!("Unknown function: {fn_name}")),
                 }
             }
@@ -582,3 +600,63 @@ impl<'a> Interpreter<'a> {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use mangle_ir::{Inst, Ir, Operand};
+
+    #[test]
+    fn test_mult_div() -> Result<()> {
+        let mut ir = Ir::new();
+        let store = MemStore::new();
+        let interpreter = Interpreter::new(&ir, Box::new(store));
+        let mut env = Env::new();
+
+        // Test fn:mult(6, 7)
+        let fn_mult = ir.intern_name("fn:mult");
+        let op6 = Operand::Const(Constant::Number(6));
+        let op7 = Operand::Const(Constant::Number(7));
+        
+        // We use Expr::Call manually
+        let expr_mult = Expr::Call {
+            function: fn_mult,
+            args: vec![op6, op7],
+        };
+
+        if let Value::Number(n) = interpreter.eval_expr(&expr_mult, &env)? {
+            assert_eq!(n, 42);
+        } else {
+            panic!("Expected number");
+        }
+
+        // Test fn:div(10, 2)
+        let fn_div = ir.intern_name("fn:div");
+        let op10 = Operand::Const(Constant::Number(10));
+        let op2 = Operand::Const(Constant::Number(2));
+        
+        let expr_div = Expr::Call {
+            function: fn_div,
+            args: vec![op10, op2],
+        };
+
+        if let Value::Number(n) = interpreter.eval_expr(&expr_div, &env)? {
+            assert_eq!(n, 5);
+        } else {
+            panic!("Expected number");
+        }
+
+        // Test fn:div(10, 0) -> Error
+        let op0 = Operand::Const(Constant::Number(0));
+        let expr_div_zero = Expr::Call {
+            function: fn_div,
+            args: vec![op10, op0],
+        };
+
+        let res = interpreter.eval_expr(&expr_div_zero, &env);
+        assert!(res.is_err());
+        assert_eq!(res.unwrap_err().to_string(), "Division by zero");
+
+        Ok(())
+    }
+}