Question

Question #21560

Answer 1

Yes, you may let `n` equal their original speed.

Explanation:

You will need the formula for speed to solve for `n`

`"speed"="distance"/"time"`

`rArr"distance"="speed"*"time"`

Let `n="initial speed"`

Then

`"final speed"=n-5`

The distance travelled to the destination is

`d_i=n*t=3.5n`

The distance travelled home is the same, but given by

`d_f=(n-5)t=4(n-5)`

Now equate the two expressions for distance and solve for n

`d_i=d_f`

`rArr3.5n=4(n-5)`

`rArr3.5n=4n-20`

`rArr0.5n=20`

`rArrn=40" "(mi)/h`