Question 1059270
An airplane has enough fuel for a 5 hour flight.
 It goes 225 mile per hour with the wind on the way out and on the return trip goes 180 mph.
 How far can the plane fly?
:
let d = the one way distance to the point of no return
:
Write a time equation, time = dist/speed
 time out + time back = 5 hrs 
{{{d/225}}} + {{{d/180}}} = 5
Find the least common multiple of 225 & 180, by prime factoring
225: 3*3*5*5
180: 2*2*3*3*5
LCM: 2*2*3*3*5*5 = 900
Multiply equation by 900
900*{{{d/225}}} + 900*{{{d/180}}} = 900*5
Cancel the denominators
4d + 5d = 4500
9d = 4500
d = 4500/9
d = 500 mi to the point of no return
;
:
See if this checks out by finding the actual time each way
500/225 = 2.22 hrs
500/180 = 2.78 hrs
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total time: 5 hrs