The distance traveled by a sound wave through a substance is proportional to time. The graph shows this relationship for several substances. Which substances have a unit rate greater than 2 km/s?
Glass and Titanium. Glass is because (10,40) (y over x) is 4 and Titanium is because (10,60) is 6 cork and lead are not since when dividing y over x it doesn't equal 2.
