Illustration by Thomson Digital

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Applying Logarithms to Everyday Life

       381–390 Use the given formula and properties of logarithms to answer the question.

      381. Orange juice has a hydrogen ion concentration of 0.001 moles/liter. What is the pH of orange juice? Use the pH formula , where H+ is the hydrogen ion concentration in moles/liter.

      382. Ammonia water has a pH of 11.6. What is its hydrogen ion concentration (in moles/liter)? Use the pH formula , where H+ is the hydrogen ion concentration in moles/liter.

      383. You invest $5,000 in an account at an annual rate of 1.475% with interest compounding quarterly. Find out how much is in the account (to the nearest cent) after 3 years by using the compound interest formula , where A is the total amount in the account in dollars, P is the principal (amount invested), r is the annual interest rate, n is the number of times compounded per year, and t is the time in years.

384. If you invest $1,000 at a rate of 3.25%, compounded continuously, how many years would it take for your money to double? Round to the nearest hundredth of a year. Use the continuous compound interest formula , where A is the amount in the account, P is the principal, r is the interest rate, and t is the time in years.

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