Answer :

The formula for compound interest is the following:

A=P(1+r/n)^nt
A=accumulated amount (what we're looking for)
P=Principal amount (initial amount). $800 in this case
r=rate. 0.09 in this case which we get from converting 9% to decimal by dividing by a 100.
n=number of times interest is compounded. In this case semi-annually which means 2
t=time. In this case 4 years
Let's calculate:
A=800(1+0.09/2)^(2*4)
A=800(1+0.045)^8
A=800(1.045)^8
A=800(1.42210061284)
A=1137.68049027
Let's round to the hundredth place (to represent cents) since the amount represents money.
Answer=The balance after 4 years will be $1,137.68

Answer:

Principal = $ 800

Time = 4 years

Rate of Interest = 9% compounded Semi Annually

          [tex]=\frac{9\pr}{2}[/tex]

Time = 4× 2=8 periods

As, we have to find balance after 4 years, so we will use the formula for amount in terms of Compound interest.

Amount(A)

      [tex]A=P[1+\frac{R}{100}]^n\\\\ A=800\times [1+\frac{9}{200}]^8\\\\ A=800 \times [\frac{209}{200}]^8\\\\ A=800 \times (1.045)^8\\\\ A=800 \times 1.422\\\\ A=1137.680[/tex]

Balance after 4 years = $ 1137.68