Question #52578

1 Answer
Mar 2, 2017

S1 = 110 (mi)/hS1=110mih; S2 = 135 (mi)/hS2=135mih

Explanation:

The speed of one of the planes can be defined as S1(mi)/hS1mih.

The speed of the second is then S2 = (S1 + 25)(mi)/hS2=(S1+25)mih.

The planes are travelling in opposite directions and are moving away from each other at the speeds above over the given time.
That means we have to ADD the speed of the two planes to arrive at the rate at which they are travelling apart.

r = S1 + (S1 + 25) = 2S1 + 25r=S1+(S1+25)=2S1+25

Here the distance is 490 mi490mi, and the time is 2h2h.

Distance traveled is defined as rate (speed) multiplied by time.

d = rtd=rt

490mi = (2S1 + 25)(mi)/h xx 2h490mi=(2S1+25)mih×2h

490 = 4S1 + 50490=4S1+50

4S1 = 490 - 504S1=49050

4S1 = 4404S1=440

S1 = 440/4 = 110(mi)/hS1=4404=110mih

S2 = (S1 + 25)(mi)/h = 135(mi)/hS2=(S1+25)mih=135mih