1. ## help me please, finding interest rates

I need help with this problem please.

Find the annual rate of growth (interest rate) on an account that was worth $150 in 1972 and$540.53 in 1994.

2. Originally Posted by takkun0486
I need help with this problem please.

Find the annual rate of growth (interest rate) on an account that was worth $150 in 1972 and$540.53 in 1994.
Let the interest rate be $x \%$, and the principal be $p$ then:
after 1 year you have: $(1+x/100)p$
after two years you have: $(1+x/100)^2p$
:
:
after $n$ years you have: $(1+x/100)^np$

Now 1972 to 1994 is 22 years, so we have:

$
540.53=(1+x/100)^{22}150
$

Which may be rewritten as:

$
1+x/100=(540.53/150)^{1/22}
$
,

or:

$
x=100[(540.53/150)^{1/22}-1]
$

RonL