Question 1077996
The speed of a sparrow is x km/h in still air. When the wind is blowing at 1 mph, the sparrow takes 5 hours to fly 12 miles to its nest and to return again. She flies out directly into the wind and returns with the wind behind her. Find her speed in still air. (Answer was 5 in the book)
--------------
Is it 12 miles each way? or 12 miles RT?
------
Using 12 miles each way:
Sparrow's airspeed is x mi/hr.
Avg speed of the round trip is
{{{2*(x+1)*(x-1)/((x+1) + (x-1))}}}
= {{{(x^2 - 1)/x}}}
{{{24/5 = (x^2 - 1)/x}}}
24x = 5x^2 - 5
5x^2 - 24x - 5 = 0
(x - 5)*(5x + 1) = 0
============
x = 5 mi/hr
x =~ 8 km/hr