Question

Two planes leave la at the same time. One heads south, while the other heads north. The southbound plane flies 50 mph slower than the northbound plane. In a .5 hour, the planes are 275 miles apart. What are the speeds

Answer 1

When two planes fly opposite to each other, the rate of separation between them is the sum of the speeds.
Let
S=speed of southbound plane 
then
S+50 mph=speed of northbound plane.
Sum of speeds = S+S+50=2S+50
If the planes are 275 miles apart in 0.5 hours, then
0.5(2S+50)=275
Isolate and solve for S
2S+50=275/0.5=550
2S=550-50=500
S=250 [south bound plane]
The northbound plane flew at S+50=300 mph.