diff --git a/src/main/java/tdd/setup/Calculator.java b/src/main/java/tdd/setup/Calculator.java
index 171f6d6..64fdadd 100644
--- a/src/main/java/tdd/setup/Calculator.java
+++ b/src/main/java/tdd/setup/Calculator.java
@@ -15,6 +15,10 @@ public String readScreen() {
     public void pressDigitKey(int digit) {
         if(digit > 9 || digit < 0) throw new IllegalArgumentException();
 
+        if (digit == 0 && latestOperation.equals("/")) {
+            throw new IllegalArgumentException("division by zero not possible");
+        }
+
         if(latestOperation.isEmpty()) {
             screen = screen + digit;
         } else {
diff --git a/src/test/java/tdd/setup/CalculatorTest.java b/src/test/java/tdd/setup/CalculatorTest.java
index 3bf16e9..46ec7b5 100644
--- a/src/test/java/tdd/setup/CalculatorTest.java
+++ b/src/test/java/tdd/setup/CalculatorTest.java
@@ -16,4 +16,37 @@ void calculatorCanDoTwoPlusTwo() {
         calc.pressEquals();
         assertEquals("4", calc.readScreen());
     }
+
+    @Test
+    @DisplayName("should display result after multiplying two positive numbers")
+    void calculatorMultiplication() {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(5);
+        calc.pressOperationKey("x");
+        calc.pressDigitKey(2);
+        calc.pressEquals();
+        assertEquals("10", calc.readScreen());
+    }
+
+    @Test
+    @DisplayName("should throw exception, when dividing by zero")
+    void calculatorShouldThrowZeroDivisionException() {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(2);
+        calc.pressOperationKey("/");
+        assertThrows(IllegalArgumentException.class, () -> {calc.pressDigitKey(0);});
+    }
+
+    @Test
+    @DisplayName("should display result after adding a digit and decimal number")
+    void calculatorCanAddDecimalNo() {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(2);
+        calc.pressOperationKey("+");
+        calc.pressDigitKey(1);
+        calc.pressDotKey();
+        calc.pressDigitKey(5);
+        calc.pressEquals();
+        assertEquals("3.5", calc.readScreen());
+    }
 }