Question

Gabrielle drives her car 300 miles and averages a certain speed if the average speed has been 7 mph less she could have traveled only 230 miles in the same length time what is the average speed

Answer 1

The average speed is 30 mph.

Explanation:

The rate of change of distance with time is speed.

i.e Speed =
`(distance)/(time)`

Let his average speed be represented by s.

Given that she covers 300 miles with an average speed.

So that;

s =
`(300)/(t)`

⇒ t =
`(300)/(s)` .................. 1

Also, if her average speed has been 7 mph less, she could have traveled only 230 miles in the same length of time. This implies that;

(s - 7) =
`(230)/(t)`

⇒ t =
`(230)/((s-7))` ............... 2

Thus equating 1 and 2, we have;

`(300)/(s)` =
`(230)/((s-7))`

230s = 300s - 2100

collecting like terms,

2100 = 300s - 230s

2100 = 70s

divide both sides by 70,

s =
`(2100)/(70)`

= 30 mph

The average speed is 30 mph.