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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?

User Hadock
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1 Answer

6 votes

Final answer:

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.

User Mithil Bhoras
by
8.5k points
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