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You are not logged in. #1 20110329 13:17:18
Please help!!  thanksBrenda drives an 18 wheeler. she plans to buy her own truck. Her research indicates that the expected running costs, C, in dollars, per 100 km, are given by C(v)=0.9 +0.0016v square, where v is the speed, in kilometers per hour. Brenda's first trip will be 1500 km, round trip. she plans to pay herself $30/h. determine the speed that will minimize Brend's cost for the trip #2 20110329 16:29:04
Re: Please help!!  thanksHi caymanisland, x is the speed in km/hr, so that cost is 30 $/hr. Any speed less than that would result in lower $/hr as well as lower cost of the trip. "Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  Buddha? "Data! Data! Data!" he cried impatiently. "I can't make bricks without clay." #3 20110329 18:59:59
Re: Please help!!  thanksHi caymanisland; v = 121.7901312369059 km/hr But like him I am forced to make some assumptions. With this model there is no minimum. In mathematics, you don't understand things. You just get used to them. I have the result, but I do not yet know how to get it. All physicists, and a good many quite respectable mathematicians are contemptuous about proof. #4 20110329 19:23:42
Re: Please help!!  thanksAnd it costs even when it's at rest. "Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  Buddha? "Data! Data! Data!" he cried impatiently. "I can't make bricks without clay." #5 20120325 11:33:48
Re: Please help!!  thanks
The answer in my textbook says it's 97.9km/h. Are you sure that's right? #6 20120325 18:47:59
Re: Please help!!  thankshi caymanisland and Naru You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei #7 20120325 18:48:38
Re: Please help!!  thanksHi Naru; In mathematics, you don't understand things. You just get used to them. I have the result, but I do not yet know how to get it. All physicists, and a good many quite respectable mathematicians are contemptuous about proof. #9 20120325 19:37:44
Re: Please help!!  thanksHi Bob; We differentiate and set to 0. Solving we get one real root of v =97.87 km / hr. That is the minimum velocity In mathematics, you don't understand things. You just get used to them. I have the result, but I do not yet know how to get it. All physicists, and a good many quite respectable mathematicians are contemptuous about proof. #10 20120326 02:43:28
Re: Please help!!  thankshi caymanisland and Naru so differentiate Set this equal to zero and rearrange This is > 0 for the calculated v so this gives a minimum. Bob You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei 