Question

Question #4ee1e

Answer 1

The answer is 30 miles per hour.

Explanation:

Use the conversion factor "60 minutes in an hour" to convert the original speed `(20"mi")/(40"min")` to miles per hour:

`(20"mi")/(40cancel("min")) * (60cancel("min"))/(1"hr")=>`

`(20"mi")/40*60/(1"hr")=>`

`(1200"mi")/(40"hr") =>`

`(30"mi")/(1"hr")`

Hence, the answer is 30 mph.

Answer 2

`30" mph"`

Explanation:

`"using the relationship"`

`color(red)(bar(ul(|color(white)(2/2)color(black)("distance (D)"="average speed (S)"xx"time (T)"color(white)(2/2)|)))`

`rArrD=ST`

`"from this we can obtain"`

`S=D/T" and "T=D/S`

`"here we require speed (S) so using "S=D/T`

`"note that time is in hours and"`

`40" minutes "=40/60" hour "=2/3" hour"`

`S=D/T=20/(2/3)=(3xx20)/2=30" miles per hour"`