Question

A person invested $200 in an account growing at a rate allowing the money to double every 13 years. How much money would be in the account after 15 years to the nearest dollar

Answer 1

445

Explanation:

y=a(2)t/d

​

a=200 d=13 t=15 d is the doubling time

y=200(2)15/13

y=445.012590439

y≈445

Answer 2

$431

Explanation:

Given parameters:

Principal = $200

Time given for the amount to double = 13yrs

Unknown:

Amount in the account after 15yrs = ?

Solution:

To solve this problem, we need to find the interest rate on this investment.

I =
`(PRT)/(100)`

I = interest

P = principal

R = Rate

T = time

Now,

if the amount should double,

Interest earned = $200

So;

200 =
`(200 x R x 13)/(100)`

200 = 26 x R

R = 7.7%

Now, in 15yrs, this amount will be;

let us find the interest;

I =
`(200 x 7.7 x 15)/(100)`

I = $231

The amount in the account will be:

Amount = Principal + Interest

Amount = $200 + $231 = $431