Item MO061003: If a student is studying how long it would take a spaceship to go between different planets in the solar system, his model should accurately represent the relative distances between the planets, but does not need to accurately represent other aspects of the solar system.
A student makes a simple model of the solar system by using a basketball to represent the sun. He then puts a series of ping pong balls in a line to represent each of the planets. The ping pong balls are spaced evenly about one foot apart from each other.
He wants to use the model to compare how long it would take for a spaceship to travel between different planets. How should he change the model to help him decide?

Distribution of Responses Percent of students responding correctly
 