Sam and Liam raced each other up and then down the hill. Sam's average speed up the hill was 1 mph, and his average speed down the hill was 9 mph. Liam ran up the hill and down the hill with the same speed, 2 mph. If the path from the bottom to the top of the hill is 1 mile long, how much time did it take each of the boys to finish - and who was the winner?

Respuesta :

So, we know that it takes Sam 1 mph up and 9 mph down and it takes Liam both 2 mph down and up the hill. So if we divide the 2 mph for Liam by 2 miles (the whole length of the hill)  we will get 1 or 1 hour. Then we do 1/1 (i don't know how to explain this part of why we do that, sorry) and than we do 1 / 9 and we get 1/9 so we add them and get 1 1/9 so that's Sam's time.

      So, Liam took one hour and Sam took 1 and 1/9 hours, in conclusion liam was faster

(I'm really sorry for my bad explaining, i tried my best)

    Sam took [tex]1\frac{1}{9}[/tex] hours and Liam took 1 hour to finish. Liam was the winner.

Given in the question,

  • Sam's average speed up the hill is 1 mph and average speed down the hill is 9 mph.
  • Liam ran up the hill and down the hill with the same speed 2 mph.
  • Length of the path from bottom to top of the hill is 1 mile.

By using the expression for the speed,

[tex]\text{Speed}=\frac{\text{Distance}}{\text{Time}}[/tex]

[tex]\text{Time}=\frac{\text{Distance}}{\text{Speed}}[/tex]

For Sam,

Time taken in going up the hill = [tex]\frac{1}{1}[/tex]

                                                   = 1 hour

Time taken in going down the hill = [tex]\frac{1}{9}[/tex] hours

Therefore, total time taken by Sam in going up and down the hill = [tex]1\frac{1}{9}[/tex] hours

For Liam,

Time taken in going up the hill = [tex]\frac{1}{2}[/tex] hours

Time taken in going down the hill = [tex]\frac{1}{2}[/tex] hours

Total time taken in going up and down the hill = [tex]\frac{1}{2}+\frac{1}{2}[/tex]

                                                                              = 1 hour

Therefore, Sam took [tex]\frac{1}{9}[/tex] hours more than Liam.

    Hence, Liam was the winner.

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