標題:
f4 maths!!!!!!!!!!PLZ HELP!
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發問:
1. Peter travels 20km in a journey. If his speed decreases by 1km/h,the journey takes 1 hour more. Find the original speed of Peter.2. A man bought a certain number of articles for $300. He sold all of them at $15 for a package of 4. If the total profit he made is the same as the original cost of 25 articles,how... 顯示更多 1. Peter travels 20km in a journey. If his speed decreases by 1km/h,the journey takes 1 hour more. Find the original speed of Peter. 2. A man bought a certain number of articles for $300. He sold all of them at $15 for a package of 4. If the total profit he made is the same as the original cost of 25 articles,how many articles did he buy? PLZ HELP!!!!!!!!!!!!!!!!!
最佳解答:
1. let x be the original speed 20/(x-1) -20/x = 1 20(1/(x-1) -1/x) = 1 20[x- (x-1)]/x(x-1) =1 20= x(x-1) x^2 -x -20=0 (x-5)(x+4) =0 x=5 or x= -4 (rej.) the original speed is 5km/h 2. let x be the no. of articles he purchased original cost per article = 300/x profits he made = 15(x/4) -300 so, (300/x)*25 =15(x/4) -300 15x/4 -300 -7500/x =0 x/4 -20 -500/x =0 x^2 -80x -2000 =0 (x-100)(x+20) =0 x=100 or x= -20 (rej.) he has brought 100 articles
其他解答:A9A3995907B431A4
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