Subject: Grade 11 math (rectangles and algebra)

Name: Kristin
Who is asking: Student
Level: Secondary

Question:
A rectangle's length is 4 more than twice its width. The area of the rectangle is 336m squared. What is its length? I just can't figure it out.

The key here is to read the question very carefully and to step your way through the English. Don't be afraid to write down three of four lines to get to the equation.

To have some notation to work with let L be the length of the rectangle and W its width. The crutial statement is "A rectangle's length is 4 more than twice its width". By stepping through the English I mean:

• A rectangle's length is 4 more than twice its width
   
  
• L is 4 more than twice W
   
  
• L is 4 more than 2*W
   
  
• L is 2*W + 4
   
  
• L = 2*W + 4

The second statement in the problem is that the area is 336 m² so L*W = 336. Substitute L from the equation above to get (2*W + 4)*W = 336.

Finally solve this equation for W and substitute the solution into L = 2*W + 4 to find the length of the rectangle.

When you solve the equation you will find that there are two solutions. Make sure that you select the solution that makes sense. Also check that you final answer has the length 4 more than twice the width and that the area is 336 m²