Question

Skylar is answering the following math problem: The value of an investment decreased by 10%. The original amount of the investment was $75.00. What is the current value of the investment? Skylar said 10% of $75.00 is $7.50, and since the investment decreased by that amount, you have to subtract $7.50 from $75.00 to arrive at the final answer of $67.50. Create one algebraic equation that can be used to arrive at the final answer of $67.50. Solve the equation to prove it results in an answer of $67.50. Be prepared to explain your thought process to the class.

Answer 1

The given parameters of the investment are;

The rate of decrease of the investment, r = -10%

The original amount of the investment, P = $75.00

Let 'A' represent the final answer (value of the investment) after the decrease in the investment, 'r', is applied, we have;

The algebraic equation that can be used to arrive at the final answer, 'A', is given as follows;

A = P + r·P

Therefore by substituting the given values, we have;

A = $75.00 + (-10/100) × $75.00 = $75.00 - 0.1 × $75.00 = $75.00 - $7.50

A = $75.00 - $7.50 = $67.50

The final amount or answer, A = $67.50

Explanation: