# Question #628c9

##### 1 Answer

Sep 4, 2015

3 Hours!

#### Explanation:

Assuming that the question defines the entire system:

Let the velocity of the first-mentioned plane be Va in miles per hour - mph West

Let the velocity of the second be Vb, similarly – mph East

Let the lapsed time be T in hours - hr

Let the distance be D in miles - mile.

Data given:

Va = 520 mph West

Vb = 540 mph East

T = 3 hr

Therefore, since the vectors, East and West, are diametrically opposite, the relative velocity is:

V = Va + Vb = 520 + 540 = 1 060 mph

Since V = D / T then, D = V x T

Therefore, D = 1 060 x 3 = 3 180 mile.