F.2 maths [Percentage] 10 點

[匿名]

2009-08-01 7:25 pm

1. Determine the annual simple interest rate at which $8500 grows to $10200 in 4 years.

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

3. Janet deposited $8000 in a bank at 5 p.a., compounded half-yearly
Find ...
(a) the interest rate per half-year,
(b) the amount for 3 years,
(c) the compound interest for 3 years.

4. A certain kind of bacteria grows steadily at a rate of 60% every 10
minutes. If there are 250 bacteria initially, find the number of bacteria after 1 hour.

5. A photocopier is bought for $15000 and its value depreciates by 16% in the first year and 9.5% in each subsequent year. Find its value at the end of the third year ( correct to the nearest dollar).

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回答 (1)

用戶10012

2009-08-01 7:55 pm

✔ 最佳答案

1.
Total interest = 10200 - 8500 = 1700
Let simple interest rate = I
so 8500 (I)(4) = 1700
I = 17/340 = 0.05 = 5%.
2.
Let principle = P, so amount = 3P, that means interest = 3P - P = 2P
so 2P = P(10%)(no. of years)
therefore no. of years = 2/10% = 2/0.1 = 20 years.
3.
(a) interest rate per half- year = 5%/2 = 2.5%
(b) Amount for 3 years = $8000(1 + 2.5%)^(3 x 2)
=8000(1.025)^6 = 9277.5
(c) Interest = 9277.5 - 8000 = 1277.5
4.
No. of bacteria after 1 hour ( 60 minutes) = 250(1 + 60%)^(60/10)
= 250(1.6)^6 = 4194.
5.
Value after 1st year = 15000(1 - 16%) = 15000(1 - 0.16)
Value after 2nd year = 15000(1 - 0.16)(1 - 9.5%)
Value after 3rd year = 15000(1 - 0.16)(1- 9.5%)(1 - 9.5%)
= 15000(0.84)(0.905)(0.905)
= 10319.72
= 10320.

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