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Susie has planned a trip to a city 60 miles away. She wishes to have an average speed of 60 miles/hour for the trip. Due to a traffic jam, however, she only has an average speed of 30 miles/hour for the first 30 miles. How fast does she need to go for the remaining 30 miles so that her average speed is 60 miles/hour for the whole trip?

Respuesta :

Answer:

90 mi/h

Step-by-step explanation:

Given,

For first 30 miles, her speed is 30 miles per hour,

Let x be her speed in miles per hour for another 30 miles,

Since, here the distance are equal in each interval,

So, the average speed of the entire journey

[tex]=\frac{\text{Average speed for first 30 miles + Average speed for another 30 miles}}{2}[/tex]

[tex]=\frac{30+x}{2}[/tex]

According to the question,

[tex]\frac{30+x}{2}=60[/tex]

[tex]30+x=120[/tex]

[tex]\implies x = 90[/tex]

Hence, she needs to go 90 miles per hour for remaining 30 miles.

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