SAT Math Multiple Choice Practice Question 248: Answer and Explanation
6. Amanda travels to work from home in 60 minutes. If, on her way home, she increases her average speed by 20% and she travels by the exact same route, how many minutes will it take her to get home?
Correct Answer: B
B This is a rate problem, so remember the basic rate formula: distance = rate × time. Start by picking a value for the distance from Amanda's home to work. No matter what distance you choose, the final answer will be the same, so choose a distance that's easy to calculate with, like 50 miles. If it takes her 60 minutes (1 hour) to get to work, she must be going 50 miles/hour. If she increases her speed by 20% for the trip home, then her speed coming home is (1.20) (50 miles/hour) = 60 miles/hour. To travel 50 miles at 60 miles/hour will take her (50 miles)/(60 mph) = 5/6 hour, which is 5/6(60 minutes) = 50 minutes.