Question

Sam walked x miles at 4mph.

Then he walked 2x miles at 3mph.
A) find average speed for the whole journey.
The second part of journey took 25mins longer than the first part.
B) Find the value of x.

Answer 1

Sam average speed for the whole journey =
`3(3)/(11) mph`

Explanation:

Formula: Speed =
`(Distance)/(Time)`

i.e. Time =
`(Distance)/(Speed)`

If Sam walked x miles at 4 mph, then time taken by him =
`(x)/(4)` hours

If he then walked 2x miles at 3 mph, then time for this period =
`(2x)/(3)`hours

Average speed =
`(Total Distance)/(Total Time)`

=
`(x+2x)/((x)/(4) (2x)/(3) )`

=
`(3x)/((x1)/(4) (2)/(3) )`

=
`(3)/((3+8)/(12) )`

=
`(3 x 12)/(11)`

=
`(36)/(11)`

=
`3(3)/(11) mph`

Hence, Same's average speed for the whole journey =
`3(3)/(11) mph`