Running at the average speed of 400m/min, Drake dashed to the end of the course. He then walked back to his starting position at an average rate of 80m/min. How long was the course if it took him 6 minutes to make the dash and walk back?
Time = distance ÷ speed so if d is the distance,
6 = d/400 + d/80
Multiply both sides by 400 to cancel the fractions
2400 = d + 5d = 6d
d = 2400 ÷ 6 m
My answer: 400
I don't know what would be the unit?
you might consider carrying the units along at each step.
(d m)/(400 m/min) = d/400 min
Makes sense, since distance/speed = time
Using your equations, multiplying
6 min * 400m/min = 2400m
makes sense, since the distance d is in meters.