Okay so first of all organize your facts and what you know.
She traveled 60 miles on the highway and 16 miles on the local roads. That's a total of 76 miles traveled altogether.
Then, on the highway she traveled 30 miles faster than in the local roads. Her speed on the local roads was 20 miles per hour.
Speed = distance / time
20 = 16 / x
20x = 16
x = 4/5 of an hour
So x is basically 48 minutes. She traveled 48 minutes on the local roads.
Now find the speed for the highway.
50mph (because she traveled 30 miles faster per hour) is the speed for the highway.
50 = 60 / x
50x = 60
x = 6/5 of an hour
So, in this case, x will be 1 hour and 12 minutes or 72 minutes.
Now that you know the distance and time traveled for both, add your values up.
Remember that speed = distance/time
So the total distance she traveled was 76 miles.
And the total time it took her to travel 76 miles was 120 minutes (by adding 48 and 72).
Now calculate for the average speed.
Speed = distance / time
Speed = 76/2 (120 minutes is 2 hours and we're looking for miles per hour here that's why 2 is placed)
Speed = 38
After dividing 76 by 2, you'll get the speed of 38.
Your answer is D) 38.
