int aPinIn = 0;            // Analogue Input on Arduino
int val = 0;               // The raw analogue value
float Vout = 0.0;          // Voltage at point between resistors
                           // (relative to ground)
float Vin = 5.0;           // Vcc (5 Volts)
float Rknown = 10000.0;    // The known resistor (10 kohms)
float Runknown = 0.0;

void setup(){

  Serial.begin(9600);
  digitalWrite(13, HIGH);

}

void loop(){

  val = analogRead(aPinIn);              // Read in val (0-1023)
  Vout = (Vin/1024.0) * float(val);      // Convert to voltage
  Runknown = Rknown*((Vin/Vout) - 1);    // Calculate Runknown

  Serial.print("Vout: ");
  Serial.println(Vout);                  // Output everything
  Serial.print("R: ");
  Serial.println(Runknown);

  delay(1000);                           // delay for readability

}