Question 465940
calculate average speed when a plane is flying from one city to another and
 is 550 miles per hour and is 430 miles per hour on the return flight.
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Let a = the average speed for the round trip
Let d = the one-way dist
:
Write a time equation: time = dist/speed
:
outbound time + return time = total time
{{{d/550}}} + {{{d/430}}} = {{{(2d)/a}}}
Actually we don't need d, just put it in here to illustrate what we are doing here
Divide thru by d, and we have:
{{{1/550}}} + {{{1/430}}} = {{{2/a}}}
Multiply by 23650a to clear the denominators, results
43a + 55a = 47300
98a = 47300
a = {{{47300/98}}}
a = 482.653 mph is the average speed
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You can confirm this solution by choosing a value for d and finding the total of the actual times.