In a certain chemical the ratio of zinc to copper is 4 and 19 a jar of the chemical contains 456 grams of copper how many grams of zinc does it contain?

Joel's and Mario's average speed is 19 kilometers per hour because it took them 1 hour to get from the campgrounds to the lake, which the speed can be found by v=d/t, in which v is velocity, d is distance, and t is for time. And the fact that it took them 2 hours, their speed is constant at the rate of 19 kilometers per hour because a round trip is from the campgrounds to the lake, which is 19 kilometers, and from the lake back to the campgrounds, which is another 19 kilometers.