how long does it take to drive 10 miles at 65 miles per hour?

You want the average speed to be 60 miles/hr i.e. It's an instinctive method you often use when you learn to play with numbers in your head. If you cant explain ANYTHING why write an explanation? Why are you setting your problem to 40 miles in 40 mins? Where did 120 come from? The only value that works is D (16 * 7.5 = 120), and thus D is the answer.ĭon't even ask me how I came to solve it with this convoluted mumbo jumbo but my brain worked on full gear and at the time that I did this it made perfect sense, even though Im not that good at explaining the whole process in hindsight.

Note that the value needs to be divided by 10 before it is multiplied by 16. We need to pick an option from A-E (which we call X), that in the denominator makes 120/(16*x) = 1.

The SECOND PART of the trip is 20 miles, and the time is 4/15 hoursīasically, the first 20 miles took 24 minutes, so the second 20 miles need to take 16 minutes in order for the average to be 60miles/h. So, the SECOND PART of the trip needs to take 4/15 hours The ENTIRE trip needs to be 2/3 hours, and the FIRST PART of the trip took 2/5 hoursĢ/3 hours - 2/5 hours = 10/15 hours - 6/15 hours

How much time was spent on this FIRST PART of the trip? So, the TIME for the ENTIRE 40-mile trip needs to be 2/3 hours.ĭriver completed the first 20 miles of a 40-mile trip at an average speed of 50 miles per hour. Solve equation to get: total time = 2/3 hours The total distance is 40 miles, and we want the average speed to be 60 miles per hour.Īverage speed = (total distance)/(total time) At what average speed must the driver complete the remaining 20 miles to achieve an average speed of 60 miles per hour for the entire 40-mile trip? (Assume that the driver did not make any stops during the 40-mile trip.) The Official Guide For GMAT® Quantitative Review, 2ND EditionĪ driver completed the first 20 miles of a 40-mile trip at an average speed of 50 miles per hour.

How long does it take to drive 10 miles at 65 miles per hour?