MATH(英)f.2

2007-08-15 8:14 am

Determine the time required for an amout of money to treble if it is deposited in a bank at a simple interest rate of 10% every year.

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更新1:

可以加以解釋嗎??? 5係好明,,

更新2:

SOR,,,,, 係10%p.a. 5係10%every year...5知有無分別..

回答 (1)

用戶150985

2007-08-15 8:27 am

✔ 最佳答案

Let the original amount of money be $y, r be the time required

y((10*r)/100)+y=3y
(0.1r+1)y=3y
0.1r+1=3
0.1r=2
r=20

It needs 20 years to treble the amount of money.

2007-08-15 00:31:47 補充：
y((10*r)/100) is the total amount of simple interest in r years;y is the original amount of money3y is the sum of money after r years( treble of the original amount of money).∵數式左右兩邊的y可以抵銷，∴不用計算金錢的真實值。

2007-08-19 22:10:04 補充：
p.a.=per annual，即每一年10%p.a. 5＝10%every year，兩者無分別

參考: me

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