Guest Posted July 4, 2008 Report Share Posted July 4, 2008 A train covers its outward journey at 90mph. It returns, over exactly the same distance, at 60 mph. What is the train’s average speed over the entire journey? its not average of 90 and 60... 60 mph journey would take longer (i dont claim this to be my own, i liked it just) Quote Link to comment Share on other sites More sharing options...
0 grey cells Posted July 4, 2008 Report Share Posted July 4, 2008 72 mph . Quote Link to comment Share on other sites More sharing options...
0 akaslickster Posted July 4, 2008 Report Share Posted July 4, 2008 61 mph.?A train covers its outward journey at 90mph. It returns, over exactly the same distance, at 60 mph. What is the train’s average speed over the entire journey? its not average of 90 and 60... 60 mph journey would take longer (i dont claim this to be my own, i liked it just) Quote Link to comment Share on other sites More sharing options...
0 Guest Posted July 4, 2008 Report Share Posted July 4, 2008 (edited) 72 mph . 1 mark for answer, you missed the other 5 from the working out Edited July 4, 2008 by plortylox Quote Link to comment Share on other sites More sharing options...
0 Guest Posted July 4, 2008 Report Share Posted July 4, 2008 75 I'm pretty sure I'm right. Quote Link to comment Share on other sites More sharing options...
0 Guest Posted July 4, 2008 Report Share Posted July 4, 2008 (edited) Average speed = Total distance divided by total time. So, if we say that the outward journey took 1 hour at 90mph, then they travelled 90 miles. Coming back that 90 miles would have taken 1.5 hours at 60mph. Total distance 180 miles divided by total travel time 2.5 hours = 72mph. Edited July 4, 2008 by Zeron Quote Link to comment Share on other sites More sharing options...
0 Guest Posted July 5, 2008 Report Share Posted July 5, 2008 72 mph Solution distance, s = 90x t(1) also, s = 60x t(2) so, 90 t(1) = 60 t(2) ===> t(2) = 1.5t(1) average speed = (s+s) / [t(1)+t(2)] = 2 x 90 x t(1) / [ t(1) + 1.5t(1)] ...............replace t(2) = 1.5t(1) here = 180 t(1) / 2.5t(1)............cancel off the t(1) = 180 / 2.5 = 72 ! Quote Link to comment Share on other sites More sharing options...
0 Guest Posted July 6, 2008 Report Share Posted July 6, 2008 shouldve replied sooner.. nicely done Woon and zeron Quote Link to comment Share on other sites More sharing options...
0 akaslickster Posted July 7, 2008 Report Share Posted July 7, 2008 (edited) shouldve replied sooner.. nicely done Woon and zeron Grey cells was the first.Correct.zeron 2nd and woon 3rd. Edited July 7, 2008 by akaslickster Quote Link to comment Share on other sites More sharing options...
Question
Guest
A train covers its outward journey at 90mph.
It returns, over exactly the same distance, at 60 mph.
What is the train’s average speed over the entire journey?
(i dont claim this to be my own, i liked it just)
Link to comment
Share on other sites
8 answers to this question
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.