maths

Question

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.

Answer 1

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