Question

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?

Answer 1

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.