My Math Forum help on distance, rate, time

 Algebra Pre-Algebra and Basic Algebra Math Forum

 December 11th, 2007, 01:46 PM #1 Newbie   Joined: Dec 2007 Posts: 1 Thanks: 0 help on distance, rate, time i have this problem for math, and i can't figure out how to get started on setting it up. jenny travels 90 kph to her cousin's house and returns the next day at 60 kph. if the whole trip took 7 hours, how far is it from jenny's house to her cousins house?
 December 11th, 2007, 06:24 PM #2 Member   Joined: Oct 2007 From: CA, USA Posts: 46 Thanks: 0 Well, this isn't such a hard problem. The distance from both houses will be the same going there as coming back. The time she takes to get there will be faster than the time she takes to get back. Since the whole trip takes 7 hours, we can use 7-t for the time she took to get back home. And it's just simple d=rt d=90t d=60(7-t) Set d equal to each other: 90t=60(7-t) Solve for t, and when you get the answer, plug it into one of the first two equations to get the distance from her house to her cousin's house.
 December 11th, 2007, 08:13 PM #3 Global Moderator   Joined: Dec 2006 Posts: 20,975 Thanks: 2224 As above, d=90t * * * * * [1] d=60(7-t) * * [2] Divide [1] by 90 and [2] by 60 and add the resulting equations to obtain d/90 + d/60 = 7, so d = 7/(1/90 + 1/60) * * * * = 252. That suggests just memorizing a simple formula for this type of problem. Compare to the problem of determining what constant voltage to apply across two resistors (90Ω and 60Ω) in parallel so that the total currrent through them is 7 amps.

 Tags distance, rate, time

 Thread Tools Display Modes Linear Mode

 Similar Threads Thread Thread Starter Forum Replies Last Post HellBunny Algebra 3 August 16th, 2012 12:46 PM Mighty Mouse Jr Algebra 4 July 9th, 2010 06:47 PM Mighty Mouse Jr Algebra 3 July 9th, 2010 03:42 PM Mighty Mouse Jr Algebra 4 June 29th, 2010 03:24 PM lak_ar Algebra 2 March 11th, 2008 12:09 PM

 Contact - Home - Forums - Cryptocurrency Forum - Top