A man drove for 4hours at a certain speed, he then doubled his speed and drove for another 3 hours.

Altogether he covered 600km. At what speed did he drive for the last 3 hours?

distance = rate x time.

d = rt
d = 160 = r*4 + 2r*3
Solve for r and 2r. 2r is the speed the last 3 hours.

Post your work if you get stuck.

I am sure DrBob meant:

600 = r*4 + 2r*3

To determine the speed at which the man drove for the last 3 hours, we can use the formula:

Speed = Distance / Time

We know that the man drove for a total of 4 + 3 = 7 hours, covering a distance of 600 km. Let's break down the problem to find the speed for each period of driving.

For the first 4 hours, we don't know the specific speed, so let's call it x. Therefore, the distance covered in the first 4 hours is:

Distance = Speed * Time
Distance = x * 4 km

For the remaining 3 hours, the man doubled his speed, so his new speed is 2x. The distance covered for the last 3 hours is:

Distance = Speed * Time
Distance = 2x * 3 km

We know that the total distance covered is 600 km, so we can equate these two distances:

Distance1 + Distance2 = 600 km
4x + 2x * 3 = 600 km

Simplifying this equation:

4x + 6x = 600 km
10x = 600 km
x = 60 km/h

Therefore, the man drove at a speed of 60 km/h for the first 4 hours. To find the speed for the last 3 hours, we double this speed:

Speed = 2 * x
Speed = 2 * 60 km/h
Speed = 120 km/h

So, the man drove at a speed of 120 km/h for the last 3 hours.