Question

Thor invests $3000 in an account, with interest compounded continuously. If his investment doubles in value after 7.2 years, what interest rate is he earning? [Use the formla A = Pert and round answer to the nearest tenth.]
A) 8.5%
B) 9.6%
C) 12.3%
D) 14.0%

Answer 1

Answer:

B.  9.6 %.

Step-by-step explanation:

A = P e^rt

His investment doubles so it comes to  3000 * 2 = $6000.

Substituting in the formula>

6000 = 3000e^7.2r   ehere r  is the interest rate.

e^7.2r = 2

Taking logs

7.2r = ln 2

r = ln2 / 7.2

r = 0.096

So the rate is 9.6%.

Answer 2

Answer:

B.  9.6 %.

Step-by-step explanation: