Robert drove at a constant rate of 60 miles per hour. He decided to drive an additional 15 miles to visit his favorite restaurant along the way for a total of 225 miles. Find the number of hours Robert spent driving. Write your answer in decimal form
Let's say Robert spent x hours driving.
In that time, he covered a distance of 60x miles.
He decided to drive an additional 15 miles, so the total distance covered was 60x + 15 miles.
We are given that the total distance covered is 225 miles.
Therefore, we can write the equation 60x + 15 = 225.
Simplifying, we get 60x = 210.
Dividing both sides by 60, we find that x = 3.5.
Therefore, Robert spent 3.5 hours driving. Answer: \boxed{3.5}.