一題超出能力範圍的方程式......

secret

題目:
   
X(1+20%)^n=20000

請大家教教我...
(其實這是一條方程式應用題，老師說可以試數，但我還是想學正式的計算方法...)

細薯

Originally posted by secret at 2005-5-2 12:18 PM:
X(1+20%)^n=20000

X is a variable??

secret

Originally posted by smallpotato226 at 2005-5-2 12:41 PM:

X is a variable??

Sorry,I made a mistake.The equation should be like that:

8000(1+20%)^n=20000

xiirr

(1+20%)^n=2.5
n log1.2=log2.5
n=log2.5 /log1.2
計算機.

secret

Originally posted by xiirr at 2005-5-2 01:29 PM:
(1+20%)^n=2.5
n log1.2=log2.5
n=log2.5 /log1.2
計算機.

但是....我的計算機沒有這項功能...(廢機...)

Echo21

8000(1 + 20%)^n=20000
9600^n = 20000
n log 9600 = log 20000
n = log 20000 / log 9600
n = 1.080044463 (10 sig. fig.)//

JOHNLAM17

Originally posted by secret at 2005-5-2 12:18 PM:
題目:
   
X(1+20%)^n=20000

請大家教教我...
(其實這是一條方程式應用題，老師說可以試數，但我還是想學正式的計算方法...)

我想問
你讀幾年班

oscar

Originally posted by Echo21 at 2005-5-2 14:10:
8000(1 + 20%)^n=20000
9600^n = 20000
n log 9600 = log 20000
n = log 20000 / log 9600
n = 1.080044463 (10 sig. fig.)//

haha！你錯了！
你告訴我：2(3)^2是不是等於6^2?

幻藍

Originally posted by oscar at 2005-5-2 06:38 PM:

haha！你錯了！
你告訴我：2(3)^2是不是等於6^2?

2(3)^2=2(9)

am I right?

JOHNLAM17

Originally posted by secret at 2005-5-2 01:14 PM:


Sorry,I made a mistake.The equation should be like that:

8000(1+20%)^n=20000

8000 * 1.2^n = 20000
1.2^n = 20000/8000
1.2^n = 2.5
n log 1.2 = log 2.5
n = 5.03 (corr. to 2 d.p.)