Students are first reminded the unit of measure for work is a joule. The amount of work to ride up the hill is estimated in context of the work of lifting an apple onto a shelf. The estimate is 10,000 joules.
Students are then asked to think about the work involved for both hill-climbing situations. The ratio of work to time is discussed. The ratio is first written using the word “to” and then as a fraction. Ask students to recall what a rate that has 1 in the denominator is called (unit rate). Ratio, rate, and unit rate are generally 6th and 7th grade concepts so they should be understood in this context.
Emphasize that by dividing numerator by denominator the answers will have a 1 in the denominator, so the unit rates can be compared. The goal is to determine which is greatest. Before calculating the unit rate, ask students to estimate their answers and choose which number will be greater.