.
- =
2400*(300+r) - 1200*(300-r) = 3*(90000-r^2)
4800r = 3*(90000-r^2)
1600r = 90000 - r^2
r^2 + 1600r - 90000 = 0.
= = .
The positive solution is r = 54.4.
Answer. 54.4 miles per hour.
Check. = 1.5 hours. ! Correct !
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It is a typical and standard "tailwind and headwind" word problem.
See the lessons
- Wind and Current problems
- Wind and Current problems solvable by quadratic equations
- Selected problems from the archive on a plane flying with and against the wind
in this site.
Also, you have this free of charge online textbook in ALGEBRA-I in this site
ALGEBRA-I - YOUR ONLINE TEXTBOOK.
The referred lessons are the part of this textbook under the section "Word problems", the topic "Travel and Distance problems".
Save the link to this online textbook together with its description
Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson
to your archive and use it when it is needed.