# Chapter 5: Chapter 5

Problem 77

Use logarithms to solve each problem. Find the interest rate needed for an investment of \(\$ 5000\) to grow to an amount of \(\$ 6000\) in 3 yr if interest is compounded continuously.

Problem 78

Use logarithms to solve each problem. Find the interest rate needed for an investment of \(\$ 4000\) to double in 5 yr if interest is compounded continuously.

Problem 79

Use logarithms to solve each problem. How long will it take an investment of \(\$ 6000\) to grow to \(\$ 7000\) if the investment earns interest at the rate of \(7 \frac{1}{2} \%\) compounded continuously?

Problem 8

How many days will it take for a sum of \(\$ 1500\) to earn \(\$ 25\) interest if it is deposited in a bank paying \(5 \% /\) year? (Use a 365-day year.)

Problem 80

Use logarithms to solve each problem. How long will it take an investment of \(\$ 8000\) to double if the investment earns interest at the rate of \(8 \%\) compounded continuously?

Problem 9

A bank deposit paying simple interest grew from an initial sum of \(\$ 1000\) to a sum of \(\$ 1075\) in \(9 \mathrm{mo}\). Find the interest rate.

Problem 9

Find the periodic payment \(R\) required to accumulate a sum of \(S\) dollars over \(t\) yr with interest earned at the rate of \(r \% / y\) year compounded \(m\) times a year. S=20,000, r=4, t=6, m=2

Problem 9

Find the present value of each ordinary annuity. \(\$ 5000 /\) year for 8 yr at \(8 \% /\) year compounded annually

Problem 9

Find the sum of the first 15 terms of the arithmetic progression $4,11,18, \ldots$