Question

I need this ASAP PLS HELP

An expression for the balance in an account is given. Use a guess, check, and revise strategy to determine the time (in years) necessary for the investment of $800 to double. (Revise your answer until it is accurate, rounded to one decimal place.)

Interest rate: 9%
800(1 + 0.09)t
t=?

Answer 1

8.0

Explanation:

The attached shows guesses until we have an answer accurate to 6 decimal places. Rounded to 1 decimal place, the answer is 8.0 years.

This (8 years) was our initial guess, based on the "rule of 72" which says the doubling time for 9% interest is 72/9 = 8 years.

Our second guess, at 8.1, was farther away from the doubled value, so the first guess at 8.0 is closer.

t = 8.0