SAT problem of the week, November 10, 2014 solution

Hint for process of elimination: In the vast majority of cases, the SAT problem creators are very careful to make solutions realistic. You may recognize 5 km, or 3.1 miles, to be the standard distance for a 5K, a very common race frequently ran or walked for charity or in local or school competition across the United States. A 5K can be run in 15 minutes for the fastest high school runners, or walked at a comfortable pace in less than one hour. Use this to eliminate the two answers that do not make sense.

Read on for a full solution.

Answer: B

Solution: Using the rate equation \text{speed} = \dfrac{\text{distance}}{\text{time}} , algebraically find Sophie’s speed:

\text{speed} = \dfrac{\text{distance}}{\text{time}} = \dfrac{0.03 \text{ km}}{0.12\text{ min}} = 0.25 \text{ km/min} = \dfrac{5 \text{ km}}{m \text{ minutes}}.

0.25 = \dfrac{5}{m} .

0.25m = 5.

m = \dfrac{5}{.25} = 20