Lucas invested $5,000 in an account to save for a trip abroad. After 7 years, his investment grew to $15,000. What is the annual interest rate, compounded continuously, that Lucas's account earned?Use the formula A=Pert, where A is the balance (final amount), P is the principal (starting amount), e is the base of natural logarithms (≈2.71828), r is the interest rate expressed as a decimal, and t is the time in years.Round your answer to the nearest two decimal places in percentage form.
Q. Lucas invested $5,000 in an account to save for a trip abroad. After 7 years, his investment grew to $15,000. What is the annual interest rate, compounded continuously, that Lucas's account earned?Use the formula A=Pert, where A is the balance (final amount), P is the principal (starting amount), e is the base of natural logarithms (≈2.71828), r is the interest rate expressed as a decimal, and t is the time in years.Round your answer to the nearest two decimal places in percentage form.
Identify Values: Identify the values for A, P, and t. A = $15,000 P = $5,000 t = 7 years
Use Formula: Use the formula A=Pert. Substitute A=15,000, P=5,000, and t=7.15,000=5,000×e7r
Isolate e7r: Divide both sides by 5,000 to isolate e7r.5,00015,000=e7r3=e7r
Take Natural Logarithm: Take the natural logarithm (ln) of both sides to solve for r.ln(3)=ln(e7r)ln(3)=7r
Divide by 7: Divide both sides by 7 to solve for r. r=ln(73)r≈0.15694
Convert to Percentage: Convert r to a percentage by multiplying by 100.r≈0.15694×100r≈15.7%So, the annual interest rate Lucas's account earned is approximately 15.7%.
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