. Suppose $8,900 is invested in an account at an annual interest rate of 5.3% compounded
continuously. How long (to the nearest tenth of a year) will it take the investment to double in
size?

Question

. Suppose $8,900 is invested in an account at an annual interest rate of 5.3% compounded 
continuously. How long (to the nearest tenth of a year) will it take the investment to double in 
size?

jim_thompson5910 · Answer

$$\Large A = Pe^{rt}$$


$$\Large A = 8900e^{0.053t}$$


$$\Large 2*8900 = 8900e^{0.053t}$$


$$\Large 2 = e^{0.053t}$$


$$\Large \ln(2) = 0.053t$$


$$\Large t = \frac{\ln(2)}{0.053}$$


$$\Large t = ???$$

anonymous · Answer

I got t=13.08? I have a really hard time with solving word problems.

jim_thompson5910 · Answer

you got it, so the final answer rounds to 13.1 years

anonymous · Answer

Thanks so much for your help!

jim_thompson5910 · Answer

np

anonymous · Answer

Do you happen to know the formula for this problem? . A candidate’s share of the votes varies directly as the number of votes cast for the candidate. 
In a city council election with four candidates, Al received 540 votes and earned a 36% share of 
the votes. Bob received 720 votes. What was Bob’s corresponding share of the votes?

jim_thompson5910 · Answer

it sounds like a ratio problem

540/36 = 720/x

solve that for x to get your answer