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quadratic equation
2009-09-24 5:40 am
Mr Tung deposited $10000 in a bank on his 25th birthday and $9000 on his 26th birthday. The interest was cmpounded yearly at r% p.a., and the total amount recieved on his 27th birthday was $22000. Find r.
回答 (1)
2009-09-24 5:47 am
✔ 最佳答案
The $10000 deposited on his 25th birthday became $10000(1 + r/100)^2 on his 27th birthdayThe $9000 deposited on his 26th birthday became $9000(1 + r/100) on his 27th birthday
Therefore 10000(1 + r/100)^2 + 9000(1 + r/100) = 22000
10000 + 200r + r^2 + 9000 + 90r = 22000
r^2 + 290r - 3000 = 0
(r - 10)(r + 300) = 0
r = 10 or r = -300(rejected)
收錄日期: 2021-04-23 23:21:05
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20090923000051KK01711