2題數學題

2007-12-14 5:14 am
我有答案,但係無詳細步驟,答案必須係我所提供的......
請認真幫我做,最好有埋中文解釋,唔好叫我自己做......
答得最好有10分。

1.永康以年利率6%存了$2500入銀行,並在1年後把所有存款提出。
若他再把本利和以相同的年利率存入銀行,求存款1年後可得的本利和。

答案:$2809

2.若年利率由5%增至8%,華安每年可多收單利息$120,問他的本金是多少?

答案:$4000

回答 (4)

2007-12-14 5:29 am
✔ 最佳答案
1.
第1提出的本利和
=年利率x本金+本金
=6%x2500+2500
=2500x(6/100)+2500
=150+2500
=2650
第2提出的本利和
=年利率x本金+本金
=6%x2650+2650
=2650x(6/100)+2650
=159+2650
=$2809
2.他的本金
=多收的單利息/增加的年利率
=120/(8%-5%)
=120/3%
=120/(3/100)
=$4000
2007-12-14 5:34 am
1. $2500x(1+6%)x(1+6%) = $2809
2. 本金 x (8% - 5%) = $120
hence 本金 = $120÷3% = $4000
2007-12-14 5:33 am
本金: P
利息: i
本利和公式: P(1+ i%)



1. 第1年: $2500x(1+6%) = $2650
之後可得的本利和: $2650x(1+6%) = $2809


2. 設本金是P
(P x 8%) - (P x 5%) = $120
0.08P - 0.05P = $120
0.03P = $120
P = $120/0.03
P = $4000
所以他的本金是$4000
參考: 自己
2007-12-14 5:29 am
1. Interest of 6% after 1 yr = 106% x 2500 = 1.06 x 2500 = 2650
Save another 1yr = 106% x 2650 = 1.06 x 2650 = 2809

2. Increase from 5% to 8% = +3%
Since 3% increment = $ 120
Let Y be the principal
3% x Y = 120
Y = 120 / 3% = 120 / 0.03 = 4000


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