Question

Andres runs 6 km on pavement and then 1 km on gravel. his speed on pavement is twice as fast as his speed on gravel. if he finishes his run in 210 min, what is his speed on the gravel surface?

Answer 1

Andres' speed on the gravel surface is approximately 1.1429 km/h.

Step-by-step explanation:

Let's assume Andres' speed on gravel is x km/h.

Since his speed on pavement is twice as fast, his speed on pavement would be 2x km/h.

Andres runs 6 km on pavement, so the time it takes him to finish this part of the run is given by time = distance / speed = 6 / (2x) = 3 / x hours.

Andres then runs 1 km on gravel, so the time it takes him to finish this part of the run is given by time = distance / speed = 1 / x hours.

The total time it takes Andres to finish his run is 210 minutes, which is equivalent to 210 / 60 = 3.5 hours.

Therefore, the total time can be expressed as 3 / x + 1 / x = 3.5.

Multiplying both sides of the equation by x gives us 3 + 1 = 3.5x, which simplifies to 4 = 3.5x.

Dividing both sides of the equation by 3.5, we find that x = 1.1429. Therefore, Andres' speed on the gravel surface is approximately 1.1429 km/h.