Question

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?

Answer 1

the avg speed is 40 i think 

Answer 2

Average speed of Jessica is 30 mph.

Explanation:

As we know the formula to calculate the average speed is

Average speed =
`\frac{\text{Total distance traveled}}{\text{Total time}}`

Jessica traveled uphill to the grocery store for 18 minutes or
`(18)/(60)` hours at 20 mph.

So the distance traveled = Speed × time

= 20 ×
`(18)/(60)`

=
`(360)/(60)=6` miles

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

Time taken in back to home =
`\frac{\text{Distance}}{\text{Speed}}`

=
`\frac{\text{6}}{\text{60}}`

= 0.1 hours

Total distance covered = 6 + 6 = 12 miles

And total time taken =
`(18)/(60)+0.1`

= 0.3 + 0.1

= 0.4 hours

Therefore, average speed of Jessica =
`\frac{\text{Total distance traveled}}{\text{Total time}}`

=
`(12)/(0.4)=30` mph

Average speed of Jessica is 30 mph.