In this tutorial we show simple step-by-step lesson on how to measure distance with an arduino microcontroller and an ultrasonic sensor. The measured distance is based on the ping time to the target of an ultrasonic ping. The measured distance is displayed via a servo and hand drawn scale. The sensor used is the virtuabotix ultrasonic sensor, and the servo is from the Sparkfun Inventor kit. Key concept in this lesson is to show students how important it is to apply what they know from Algebra related to lines in order to map inputs (distance measurements) onto outputs (servo angle).