Question

Clifton drove for 3 hours at 52 mph. How fast must he drive during the next hour in order to have an average speed of 55 mph?

Answer 1

64 mph

Explanation:

Given that:

Speed for the first 3 hours = 52 mph

Average speed for 4 hours = 55 mph

To find:

Speed for the next hour = ?

Solution:

Formula for average speed is given as:

`Average\ Speed = (Total\ Distance)/(Total \ Time \ Taken)`

Formula for Distance:

`Distance =Speed * Time`

Distance traveled in first 3 hours:

`Distance =52* 3 = 156\ miles`

Let the speed for the next hour = u mph

Distance traveled in 1 hour =
`u * 1 = u\ miles`

Total distance traveled = (156 + u) miles

Total time = 4 hours

Average Speed = 55 mph

Putting the values in formula:

`55 = (156+u)/(4)\\\Rightarrow 220 = 156+u\\\Rightarrow \bold{u = 64\ mph }`

So, the answer is: 64 mph