Learning Resources

Focus G: Using the Quadratic Formula to Solve Problems

Test yourself (Answers)

Step 1 : Summarize the Situation

The information in this problem can best be summarized by drawing a diagram and placing the information on it.

Step 2 : Decide How to Solve the Problem

Write an expression for the area that is not electroplated (the white area) and let it equal 140.

Step 3 : Set up an Equation that can be solved

 x(24 - x) = 140

Step 4 : Solve the Equation

           x(24 - x) = 140

             24x - x² = 140

-x² +24x - 140 = 0

x² - 24x + 140 = 0

(x -10)(x - 14) = 0

     x = 10   or  x = 14

Step 5 : Interpret the Solution to the Equation in Context

The width of the metal strip could be 10 cm or 14 cm. Both answers are possible in this context. (It is left to you to draw a diagram to scale showing the two possible pieces of sheet metal.)