Amy bought a dog at $x and then sold it at $1500 later. If her profit per cent is x% , find the value of x.
(Given your answer correct to 3 significant figures)
F.4 Maths (20)
2007-10-29 8:08 am
回答 (3)
2007-10-29 8:16 am
✔ 最佳答案
[(1500 - x) / x ] x 100% = x %[100(1500 - x)] / x = x
150000 - 100x = x^2
x^2 + 100x - 150000 = 0
By the quadratic formula,
x = {(-100) + squareroot[(100)^2 - 4(1)(-150000]}/(2x1) or x = {(-100) - squareroot[(100)^2 - 4(1)(-150000]}/(2x1)
x = 340.51 or x = -440.51 (rejected)
x = 341 (corrected to 3 sig. fig.)
If there is a mistake, please inform me.
參考: My Maths knowledge
2007-10-29 8:28 am
(1500 - x) / x X 100% = x%
(1500- x) / x X 100 = x
(1500-x)100 = x^2
x^2 + 100x - 150000 = 0
由於x = [-b+/- ( b^2 - 4ac)^1/2] / 2a
所以x = [ -100+/- ( 100^2+600000)^ 1/2] / 2
x= 340 or -440(rejected)
所以x =340
(1500- x) / x X 100 = x
(1500-x)100 = x^2
x^2 + 100x - 150000 = 0
由於x = [-b+/- ( b^2 - 4ac)^1/2] / 2a
所以x = [ -100+/- ( 100^2+600000)^ 1/2] / 2
x= 340 or -440(rejected)
所以x =340
參考: 自己
2007-10-29 8:19 am
((1500 - x) / x) * 100 = x
=> 150000 - 100x = x^2
=> x^2 + 100x - 150000 = 0
=> x = 340 (3 sig. fig.) or x = -441 (rejected)
2007-10-29 00:21:43 補充：
should be 341, sorry
=> 150000 - 100x = x^2
=> x^2 + 100x - 150000 = 0
=> x = 340 (3 sig. fig.) or x = -441 (rejected)
2007-10-29 00:21:43 補充：
should be 341, sorry
收錄日期: 2021-04-13 14:14:37
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20071029000051KK00034