find r when p = $800, i = $110, and t = 2 years, 6 months

Question

find r when p = $800, i = $110, and t = 2 years, 6 months

Answer 1

p = $800, i = $110, and t = 2 years, 6 months

S.I=P*r*t/100

so,

110=800*R*2.5/100

110=2000*r/100

or, R=110*100/2000

R=11000/2000

R=5.5%

 

Answer 2

This looks like an interest problem. The basic formula is: I = Prt, where I is the interest earned, P is the principle or beginning amount, r is the interest rate in a decimal, and t is the time in years. So, for this one, you have 110 = 800 * r * 2.5 You are apparently looking for the interest rate. Simplify each side, and then divide and change into a percent to solve.

Answer 3

I(interest)  =  P(principal)exp(kt)

A (total amount)  = I  +  P  =  P(expkt   +   1), t  =  2.5 years (2 yr, 6 mo)

k  =  (ln (A/P))/t  =  ln(910/800)/2.5  =  .0515, or 5.15% interest.