Suppose you deposit $5,000 in savings account that earns 3% annual interest. If you make no other withdrawals or deposits, how many years will it take the account balance to reach at least $6,000?

a) 10 years

b) 6 years

c) 7 years

d) 4 years

1 answer

We can use the formula for compound interest to solve this problem:

A = P(1 + r/n)^(nt)

where:

A = the final amount (in this case, $6,000)
P = the principal amount (in this case, $5,000)
r = the annual interest rate (3%)
n = the number of times the interest is compounded per year (we'll assume it's compounded annually, so n = 1)
t = the number of years

Plugging in the values we know, we get:

6,000 = 5,000(1 + 0.03/1)^(1t)

Simplifying:

1.2 = (1.03)^t

Taking the natural logarithm of both sides:

ln(1.2) = t ln(1.03)

Dividing both sides by ln(1.03):

t = ln(1.2) / ln(1.03) ≈ 7.22

So it will take about 7 years for the account balance to reach at least $6,000. The answer is c) 7 years.