Question

Roberta deposited $3,116.92 into a savings account with an interest rate of 3.9% compounded quarterly. About how long will it take for the account to be worth $7,000?

Answer 1

Options:
a) 14 years, 5 months
b) 20 years, 10 months
c) 21 years, 2 months
d) 29 years, 11 months

Answer 2

Use the Formula, A = P(1 + i/n)^(nt)
A is the eventual amount, P is the Principal amount, i is the interest expressed as a decimal, n is the number of times the interest is compounded per time period and t is the number of time periods.

7000 = 3116.92(1 + 0.039/4)^4t
7000= 3116.92(1.00975)^4t
7000/3116.92 = 1.00975^4t
2.24581= 1.00975^4t
log on both side
4tLog 1.00975 = Log 2.24581
4t ≈ 83.385

Answer 3

can you solve for t now?

Answer 4

I dont understand the log thingy... :/

Answer 5

the answer will be 20 years and 10month.... but i want to understand how you got to:
4t ≈ 83.385 (like, how do you solve the log, and why u used it? )