# maths

a sum of money doubles in 20 years on simple interest. it will triple at the same rate in ?

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1. 2=1(1+i)^20
take the log of each side
log2=20(log(1+i)
log(1+i)=log2/20=.01505
now take the antilog
1+i=10^(.01505)=1.03526
so i=3.526 percent

triple?
3=(1.03526)^t
take the log of each side
log3=t*log(1.03526)
t= log3/log(1.03526)= .4771 /.01505
almost 32 years

check that

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2. 60

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posted by zafar

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