<PRE><B>Question 1039408</B>
f = p(1+r)^n where f is the future value, p is the present value, r is the interest rate and n is the number of periods

5200 = p (1+r)^5
5680 = p(1+r)^7

From 5200 = p (1+r)^5
 we calculate p

p = 5200/(1+r)^5

Similarly we calculate p from
5680 = p(1+r)^7

and we get p = 5680/(1+r)^7

We set the two equations together since both are equal to p

5200/(1+r)^5 = 5680/(1+r)^7

5680/5200 = (1+r)^7 divided by (1+r)^5
(1+r)^2 = 1.0923
Square root of 1.0923 is 1.045

1+r = 1.045
therefore r - 1.045 - 1 = .045 = 4.5%


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