中3百分率 - Ans.fyi 參考答案

中3百分率

2007-10-21 3:43 am

David have just borrow $80000 from a bank at an interest rate of 12%p.a.compounded monthly. If he repays $25000 at the end of each month,how much hill he owe the bank at the end of the thrid month?

Mary deposited some money at the bank.She earned $720 simple interest in 18months. If the interest rate was 12%%p.a.,find the principal

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abaform

2007-10-21 5:28 pm

✔ 最佳答案

At the end of the first month, the money he owes the bank
= $80000 * (1 + 12% / 12) - $25000
= $80000 * 1.01 - $25000
= $55800

At the end of the second month, the money he owes the bank
= $55800 * (1 + 12% / 12) - $25000
= $55800 * 1.01 - $25000
= $31358

At the end of the third month, the money he owes the bank
= $31358 * (1 + 12% / 12) - $25000
= $31358 * 1.01 - $25000
= $6671.58

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Let $x be the principal
x * 12% * (18/12) = 720
x * 0.18 = 720
x = 720 / 0.18 = 4000
The principal is $4000.

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