Alex and Jane each start from the same position, heading East and North respectively. If Alex walks at 3 miles per hour and Jane walks 33.3% faster than him, approximately how fast are their distance growing apart?

a. 3 miles per hour

b. 4 miles per hour

c. 5 miles per hour

d. 6 miles per hour

e. 7 miles per hour

***I forgot how to put together these types of equations... could you please walk me through it? Thanks!! :)

Question

Alex and Jane each start from the same position, heading East and North respectively. If Alex walks at 3 miles per hour and Jane walks 33.3% faster than him, approximately how fast are their distance growing apart?

a.  3 miles per hour

b.  4 miles per hour

c.  5 miles per hour

d.  6 miles per hour

e.  7 miles per hour

***I forgot how to put together these types of equations... could you please walk me through it? Thanks!! :)

anonymous · Answer

c. 5 miles per hour

anonymous · Answer

do you want to know why?

anonymous · Answer

First diagram the problem.  Jane is going North.  Alex is going East.  So place them in a Cartesian plane.  See drawing:|dw:1381181118623:dw|

anonymous · Answer

Alex is going 3 mph and Jane walks 33% faster, so using Speed_A for Alex's speed and Speed_J for Janes speed, we use the relative speed equation:
$$Speed_A \times 1.33 = Speed_J$$
Plug in $$Speed_A = 3 mph$$
to get
$$Speed_J = 4 mph $$

anonymous · Answer

I don't know how much physics you know, but formally Alex and Jane have velocity vectors of (3,0) and (0,4) respectively.  They make line segments approximately like those in this drawing.  The total distance between them is calculated by finding the hypotenuse of a right triangle with legs of 4 and 3.
|dw:1381181682925:dw|

anonymous · Answer

ohhh okay, i see... that helped a lot. thanks so much!! :)

anonymous · Answer

oh sorry, i just wanted to make sure, so for these kinds of problems, we end up having to create a triangle and use the pythagorean theorem to solve?