Dave walked to his friend's house at a rate of 4 mph returned back biking at a rate of 10 mph. If it took him 18 minutes longer to walk than to bike, then what was the total distance of the round trip?
Let the distance to his friend's house be d.
The time it took Dave to walk to his friend's house is d/4 hours.
The time it took Dave to bike back is d/10 hours.
Since it took him 18 minutes longer to walk than to bike, then d/4 = d/10 + 18/60, or 3d/5 - d/2 = 18/60.
Multiplying through the equation by 60 gives 36d - 30d = 18, or 6d = 18.
Hence, the total distance of the round trip is 2d = 2 × (18/6) = <<2*18/6=6>>6 miles. Answer: \boxed{6}.
Try again
Let the total distance of the round trip be d miles.
The time it took Dave to walk to his friend's house is d/4 hours.
The time it took Dave to bike back is d/10 hours.
Since it took him 18 minutes longer to walk than to bike, we can write the equation d/4 = d/10 + 18/60.
Multiplying through the equation by 20 gives 5d = 2d + 6.
Combining like terms gives 3d = 6.
Dividing both sides by 3 gives d = 2.
Therefore, the total distance of the round trip is 2 miles. Answer: \boxed{2}.
No!
I apologize for the mistake. Let's try again.
Let the distance to his friend's house be d.
The time it took Dave to walk to his friend's house is d/4 hours.
The time it took Dave to bike back is d/10 hours.
Since it took him 18 minutes longer to walk than to bike, we can write the equation d/4 = d/10 + 18/60.
Multiplying through the equation by 20 gives 5d = 2d + 6.
Combining like terms gives 3d = 6.
Dividing both sides by 3 gives d = 2.
Therefore, the distance to his friend's house is 2 miles.
The round trip distance is 2 * 2 = 4 miles. Answer: \boxed{4}.