Question

An investor deposits $9000 into an account that earns simple interest at 5.45% annually. the amount a (in dollars) in the account is calculated using the formula nr019-1.jpg in the formula, p is the principal (in dollars), r is the interest rate (in decimal form), and t is the time (in years). how much interest is gained on the investment after 3 months?

Answer 1

we know that
the formula for calculating simple interest is
I=P*r*t
A=P*[1+r*t]
where
I is the simple interest
A is the amount in dollars
P is is the principal (in dollars)
r is the interest rate (in decimal form)
t is the time (in years)

in this problem
P=$9000
r=5.45%-----> r=0.0545
t=3 months------> t=3/12-----> t=0.25 year

substitute in the formula
A=P*[1+r*t]-----> 9000*[1+0.0545*0.25]-----> 9000*[1.013625]
A=$9122.625
I=P*r*t------> 9000*0.0545*0.25------> I=$122.625
or also
interest =$9122.625-$9000------> $122.625

the answer is
$122.625