Question

# At 6.1 percent interest, how long does it take to double your money? (Do not round...

At 6.1 percent interest, how long does it take to double your money? (Do not round intermediate calculations and round your answer to 2 decimal places, e.g., 32.16.) Length of time years At 6.1 percent interest, how long does it take to quadruple it? (Do not round intermediate calculations and round your answer to 2 decimal places, e.g., 32.16.) Length of time years.

a.We use the formula:
A=P(1+r/100)^n
where
A=future value(\$2x)
P=present value(\$x say)
r=rate of interest
n=time period.

2x=x*(1.061)^n

2=(1.061)^n

Taking log on both sides;

log 2=n*log (1.061)

n=log 2/log (1.061)

=11.71 years(Approx)

b.We use the formula:
A=P(1+r/100)^n
where
A=future value(\$4x)
P=present value(\$x say)
r=rate of interest
n=time period.

4x=x*(1.061)^n

4=(1.061)^n

Taking log on both sides;

log 4=n*log (1.061)

n=log 4/log (1.061)

=23.41 years(Approx)

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