The correct answer is 90 miles per hour
Step-by-step explanation:
The first step to know how fast Emily needs to drive to get 10 minutes earlier is to determine the distance from her work to her home. This can be calculated by using the information provided (speed and time). The process is shown below:
speed = distance ÷ time
distance = speed x time
distance = 60 miles per hour x 0.5 (30 minutes represent 0.5 hours)
distance= 30 miles
Now, using the same formula let's calculate the speed for 20 minutes (30 minutes - 10 minutes earlier = 20 minutes)
speed = distance ÷ time
speed = 30 miles ÷ 0.333 (20 minutes represents 0.333 hours as 20 minutes is 1/3 of an hour)
speed= 90 miles per hour