標題:
maths
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發問:
Mr.Tang deposited $10000 in a bank at the beginning of 2012 and $9000 at the beginning of 2013. The interest was compounded yearly at r% p.a. , and total amount he received at the beginning of 2014 was $22000. Find r.
最佳解答:
10000(1+r%)2+9000(1+r%)=22000 ==> 10(1+r%)2+9(1+r%)-22=0==> [10(1+r%)-11][(1+r%)+2]=0==> 1+r%=1.1 or -2 (rej)==> r%=0.1==> r=10
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