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Starting at home, Jessica traveled uphill to the grocery store for 18 minutes at just 20 mph. She then traveled back home along the same path downhill at a speed of 60 mph.
What is her average speed for the entire trip from home to the grocery store and back?

Respuesta :

the avg speed is 40 i think 

Answer:

Average speed of Jessica is 30 mph.

Step-by-step explanation:

As we know the formula to calculate the average speed is

Average speed = [tex]\frac{\text{Total distance traveled}}{\text{Total time}}[/tex]

Jessica traveled uphill to the grocery store for 18 minutes or [tex]\frac{18}{60}[/tex] hours at 20 mph.

So the distance traveled = Speed × time

                                         = 20 × [tex]\frac{18}{60}[/tex]

                                         = [tex]\frac{360}{60}=6[/tex] miles

Now she traveled back with same path with the speed of 60 mph.

Time taken in back to home = [tex]\frac{\text{Distance}}{\text{Speed}}[/tex]

                                               = [tex]\frac{\text{6}}{\text{60}}[/tex]

                                               = 0.1 hours

Total distance covered = 6 + 6 = 12 miles

And total time taken = [tex]\frac{18}{60}+0.1[/tex]

                                  = 0.3 + 0.1

                                  = 0.4 hours

Therefore, average speed of Jessica =  [tex]\frac{\text{Total distance traveled}}{\text{Total time}}[/tex]

                                                             = [tex]\frac{12}{0.4}=30[/tex] mph

Average speed of Jessica is 30 mph.