Problema Solution
A passenger plane left Los Angeles and flew toward Dublin at an average speed of 168 mph. Some time later a jet left flying in the opposite direction with an average speed of 316 mph. After the passenger plane had flown for eight hours the planes were 3240 miles apart. Find the number of hours the jet flew.
Answer provided by our tutors
Let
v1 = 168 mph is the speed of the passenger plane
v2 = 316 mph is the speed of the jet
t1 = 8 h the hours that the passenger plane was flying
After time of t 1= 8 hours the distance between the planes was S = 3240 miles
We need to find t2 = the hours that the jet plane was flying.
the distance that the passenger plane has crossed S1 = v1*t1 = 168*8 = 1344 miles
the distance that the jet plane has crossed S2 = v2*t2 = 316*t2 miles
Because they are flying in opposite directions the passed distance is equal to the distance apart that is 3240 miles. Thus we have
S1 + S2 = S
S1 + S2 = 3240
1344 + 316*t2 = 3240
1344 + 316*t2 = 3240 - 1344
t2 = 6 hour
The jet was flying 6 hours