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April 28, 2015

April 28, 2015

Posted by **mac** on Friday, July 22, 2011 at 9:38am.

- math -
**bobpursley**, Friday, July 22, 2011 at 10:03amlet d be the shorter distance.

d+26=(r+5)4.2 (4.2 hrs is 4hrs 12min)

d=r*4

two equations, two unknowns, solve for d.

- math -
**Reiny**, Friday, July 22, 2011 at 10:22amlength of shorter trip ---- x miles

speed for shorter trip ---- 4/x mph , since speed = distance/time

length of longer trip --- x+26

speed for longer trip --- 21/(5(x+26)) .....explanation : ( 21/5 hrs = 4hr. 12 min )

21/(5(x+26)) - 4/x = 5 , ... the difference is their speeds is 5 mph

multiply by 5x(x+26)

21x - 20(x+26) = 25x(x+26)

21x - 20x - 520 = 25x^2 + 650x

25x^2 + 649x + 520=0

x = (-649 ± 607.619)/50

this gave me two negative answers, but x has to be > 0

Unless I made some silly arithmetic error, this problem has no solution.

- Go with bobpursley - math -
**Reiny**, Friday, July 22, 2011 at 10:38amNever mind my solution, go with bobpursley

Found my "silly error" , just noticed I had my fractions upside - down. e.g. speed for shorter trip = x/4 , etc.

Can I blame it on the heat affecting my brain ?

- math -
**mac**, Friday, July 22, 2011 at 11:58amcould bob pursley finish the problem ? i still don't have the answer or could you, reiny, do it again without the error. i need to see the problem worked, thanks.

- math -
**bobpursley**, Friday, July 22, 2011 at 1:04pmYes, I could finish it, however, you dont want anyone thinking you are an answer grazer. You do the work, and I will critique it.

- math -
**mac**, Friday, July 22, 2011 at 5:48pmmr. pursley, Have you ever worked geo. & trig. etc with the heat on wheather you blew up the town or the target or the building collapased or was built in the right place. i'm not an answer graser. you don't know how long i worked on this problem. i'm trying to learn some different types of math now for fun. if you choose to not assist, please don't.