distance-rate-time,interest,average,cost

Question

Two planes, which are 2340 miles apart, fly toward each other. Their speeds differ by 35 mph. If they pass each other in 4 hours, what is the speed of each?

Answer 1

distance=rate*time

2340=r*4+(r+35)*4

2340=4r+4r+140

2340=8r+140

2340-140=8r

2200=8r

r=2200/8

r=275 mph

r+35=310 mph

Answer 2

x = plane 1 speed

y = plane 2 speed

4x = distance of plane 1

4y = distance of plane 2

 

x-y = 35

4x+4y = 2340

 

Divide second equation by 4........

 

x-y = 35

x+y = 585

 

Add two equations together:

 

2x = 620

x= 310 mph

y = 310-35 = 275 mph