Subject: Plane Problem Date: Sat, 06 Mar 1999 18:22:17 PST
Math Central: A plane left New York and headed East to its destination 3600 miles away across the Atlantic. On the way back its speed was boosted by a 50 mph tail wind and it arrived an hour early. What was its normal speed? If you could help that would be great!
Thanks!
Hi, We know that Distance = Speed x Time so we know that
If we let the usual speed be x mi/h (x > 0), then the new speed is x + 50 mi/h. So
and
Thus we know that
You can now solve for x. If I were going to solve for x I would multiply both sides of the equation by x(x + 50) to "eliminate" the denominators. This leads to a quadratic equation that can be solved by factoring or by using the quadratic formula. You will likely find that one of the roots is negative. If so, then it is inadmissible since x > 0.
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