document.write( "Question 287285: Plane 1 can travel 1400 miles in 1 hour less time than it tales plane B to travel 2000 miles. The rate of plane B is 50 miles per hour greater than the rate of plane A. Find the times and rates of both planes. \n" ); document.write( "
Algebra.Com's Answer #208243 by ankor@dixie-net.com(22740) You can put this solution on YOUR website! Plane 1 can travel 1400 miles in 1 hour less time than it tales plane B to travel 2000 miles. \n" ); document.write( "The rate of plane B is 50 miles per hour greater than the rate of plane A. \n" ); document.write( " Find the times and rates of both planes. \n" ); document.write( ": \n" ); document.write( "Let r = the rate of plane A \n" ); document.write( "then \n" ); document.write( "(r+50) = the rate of plane B \n" ); document.write( "; \n" ); document.write( "Write a time equation, Time = dist/rate \n" ); document.write( ": \n" ); document.write( "Plane B time - Plane A time = 1 hr \n" ); document.write( " \n" ); document.write( "Multiply by r(r+50); results \n" ); document.write( ": \n" ); document.write( "2000r - 1400(r+50) = r(r+50) \n" ); document.write( ": \n" ); document.write( "2000r - 1400r - 70000 = r^2 + 50r \n" ); document.write( ": \n" ); document.write( "600r - 70000 = r^2 + 50 \n" ); document.write( "Arrange as a quadratic equation \n" ); document.write( "0 = r^2 + 50r - 600r + 70000 \n" ); document.write( ": \n" ); document.write( "r^2 - 550r + 70000 = 0 \n" ); document.write( "Factor \n" ); document.write( "(r - 350)(r - 200) = 0 \n" ); document.write( "Two solutions \n" ); document.write( "r = 200 mph for plane A; then 250 mph for plane B \n" ); document.write( "and \n" ); document.write( "r = 350 mph for plane A; then 400 mph for plane B \n" ); document.write( ": \n" ); document.write( "Both these solutions will work \n" ); document.write( ": \n" ); document.write( "Find the times when Plane A = 200 mph \n" ); document.write( "B: 2000/250 = 8 hr \n" ); document.write( "A: 1400/200 = 7 hr \n" ); document.write( ": \n" ); document.write( "find the times when Plane A = 350 mph \n" ); document.write( "B: 2000/400 = 5 hr \n" ); document.write( "A: 1400/350 = 4 hr \n" ); document.write( " |