Sam drove for 2 hours at 45mph. He has the same distance remaining. How fast should he drive to make his average speed 60mph.
distance covered in first leg = 2(45) or 90 km
so total distance = 180 km
wants to average 60 mph
total time = 180/60 = 3
so he must cover the last 90 km in 1 hour or his speed must be 90 kmh.
To find out how fast Sam should drive to make his average speed 60mph, we need to first determine the distance he has already covered. We know that Sam drove for 2 hours at 45mph. So, the distance covered can be calculated using the formula: distance = speed × time.
Distance covered = 45mph × 2 hours = 90 miles
Since Sam has the same distance remaining, the total distance he needs to travel is 2 times the distance he has already covered, which is 2 × 90 miles = 180 miles.
To calculate the average speed, we use the formula: average speed = total distance ÷ total time. We want the average speed to be 60mph and we know the total distance is 180 miles. To find the total time, we rearrange the formula as follows:
total time = total distance ÷ average speed
total time = 180 miles ÷ 60mph = 3 hours
Now, since Sam has already driven for 2 hours, he has just 3 - 2 = 1 hour remaining to cover the remaining distance.
To find out how fast Sam should drive in this remaining time, we use the formula: speed = distance ÷ time.
speed = 180 miles ÷ 1 hour = 180 mph
Therefore, Sam should drive at 180mph to make his average speed 60mph.