title: Error: Exception in thread "main" java.lang.NumberFormatException: For input string: "kotlin.Unit"
body: <p>I am trying to print the result as a double and receive the following error:-</p>
  
  <p>Exception in thread "main" java.lang.NumberFormatException: For input string: "kotlin.Unit"</p>
  
  <p>How would I fix this?</p>
  
  <pre><code>calculateWeight(150.0).toString().toDouble()
  }
  fun calculateWeight(bodyWeight: Double) {
      val mercury = bodyWeight * 0.38
      val venus = bodyWeight * 0.91
      val earth = bodyWeight * 1.00
      val mars = bodyWeight * 0.38
      val jupiter = bodyWeight * 2.34
      val saturn = bodyWeight * 1.06
      val uranus = bodyWeight * 0.92
      val neptune = bodyWeight * 1.19
      val pluto = bodyWeight * 0.06
  
      println("My body weight is $bodyWeight pounds and on the different planets it equals:\n" +
                  "Mercury: $mercury, \nVenus: $venus, \nEarth: $earth, " +
                  "\nMars: $mars, \nJupiter: $jupiter, \nSaturn: $saturn, \nUranus: $uranus," +
                  "\nNeptune: $neptune, \nPluto: $pluto")
  </code></pre>