Free help with homework

Why join Brainly?

  • ask questions about your assignment
  • get answers with explanations
  • find similar questions

5/6th of the way across a narrow railroad bridge, Anoop hears a train coming towards him. He knows that the train's speed is 35 miles per hour and that he

has just enough time to reach safety at either end of the bridge. How fast can Anoop run (in miles per hour)?



This Is a Certified Answer

Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
See diagram.

let the bridge be L miles long.  Let Anoop run v miles per hour.

Hence by the time Anoop runs to EITHER END of the railroad bridge, the train just comes to the SAME end of the bridge.
1)  Anoop runs L - 5L/6 = L/6 distance,  to the nearer end of the bridge.
     The train has to run through the distance x.

\frac{L/6}{v} = \frac{x}{35}\ \ \ \ => \ \ v = \frac{35 L}{6 x}, \ \ \ - equation 1

2)  Anoop runs 5L/6 to the farther end of the bridge.

\frac{L+x}{35} = \frac{5L/6}{v},\ \ \ => \ v = \frac{35*5 L}{6 (L+x)}, \ - equation\ 2

   divide equation 2  by equation 1  =>
 1 = \frac{5 x}{L+x},\ \ => \ L + x = 5 x,\ \ \ L=4\ x,\ \ \ - equation3 

     substitute in equation 1,
 v = \frac{35 * 4 x}{6 * x} = \frac{140}{6} = 23.66 mph\\

Anoop can run at 23.66 mph

0 0 0
The Brain
  • The Brain
  • Helper
Not sure about the answer?
Learn more with Brainly!
Having trouble with your homework?
Get free help!
  • 80% of questions are answered in under 10 minutes
  • Answers come with explanations, so that you can learn
  • Answer quality is ensured by our experts