maths
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.
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- 螞蟻雄兵Lv 75 年 前最佳解答
Mr.Tang deposited $10000 in a bank at thebeginning 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.
Sol
10000(1+r/100)^2+9000(1+r/100)=22000
Set p=1+r/100
10000p^2+9000p=22000
10p^2+9p-22=0
(10p-11)(p+2)=0
p=11/10 or p=-2(reject)
r/100=1/10
r=10
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