1. ## Average Speed

If I drive x mph for t hours and then y mph for 2t hours, what is the expression for average speed?

I know the average speed = distance/time but that's where I get stuck.

2. Originally Posted by magentarita
If I drive x mph for t hours and then y mph for 2t hours, what is the expression for average speed?

I know the average speed = distance/time but that's where I get stuck.

Hi . You will need to look for the total distance first .

Use the formula s=vt (ie s=xt and s=y2t)

average speed = (xt+y2t)/(2t+t)

3. Originally Posted by magentarita
If I drive x mph for t hours and then y mph for 2t hours, what is the expression for average speed?

I know the average speed = distance/time but that's where I get stuck.
$\displaystyle d=x\times t+y \times 2t$

$\displaystyle t=t+2t=3t$

$\displaystyle \overline{v}=\frac{xt+2yt}{3t}$

CB

4. Originally Posted by magentarita
If I drive x mph for t hours and then y mph for 2t hours, what is the expression for average speed?

I know the average speed = distance/time but that's where I get stuck.
Find the distance covered when you drive x mph for t hours and y mph for 2t hours, then add them to get total distance

EDIT : a minute late from CB and two minutes from mathaddict...

5. Originally Posted by magentarita
If I drive x mph for t hours and then y mph for 2t hours, what is the expression for average speed?

I know the average speed = distance/time but that's where I get stuck.
Or... d = rt.

If you drive x mph for t hours, then the distance traveled is xt miles.
If you drive y mph to 2t hours, then the distance traveled is 2yt miles.
Total distance: xt + 2yt.
Total time: t + 2t = 3t.

Average speed:
$\displaystyle \frac{xt + 2yt}{3t} = \frac{x + 2y}{3}$

01

Edit: beaten to it by three people!

6. Originally Posted by yeongil
Edit: beaten to it by three people!
LOL !!
even i'm surprised when i know you also give the answer

7. ## Thanks..

I want to thank all of you.