Example

Finding Rectangle Dimensions Using a 'More Than Twice' Relationship

Apply the geometry problem-solving strategy when one dimension of a rectangle is described using both multiplication and addition relative to the other — a step up from problems where the relationship involves only addition or subtraction.

Problem: The length of a rectangle is four centimeters more than twice the width. The perimeter is 3232 centimeters. Find the length and width.

  1. Read: A rectangle has P=32P = 32 cm, and its length is four more than twice its width.
  2. Identify: The length and width of the rectangle.
  3. Name: Let ww = the width. The phrase "four more than twice the width" combines two operations: twice signals multiplication by 22, and four more than signals adding 44. So the length is 2w+42w + 4. Draw and label the rectangle with width ww and length 2w+42w + 4.
  4. Translate: Write the perimeter formula and substitute:

P=2L+2WP = 2L + 2W

32=2(2w+4)+2w32 = 2(2w + 4) + 2w

  1. Solve: Distribute: 32=4w+8+2w32 = 4w + 8 + 2w. Combine like terms: 32=6w+832 = 6w + 8. Subtract 88 from both sides: 24=6w24 = 6w. Divide both sides by 66: 4=w4 = w. The width is 44 cm. Find the length: 2(4)+4=8+4=122(4) + 4 = 8 + 4 = 12. The length is 1212 cm.
  2. Check: P=2(12)+2(4)=24+8=32P = 2(12) + 2(4) = 24 + 8 = 32, and 32=3232 = 32 \checkmark
  3. Answer: The length is 1212 cm and the width is 44 cm.

Unlike problems where one dimension differs from the other by a simple constant (e.g., "two less than the length"), this problem's relationship involves both multiplication and addition — the expression 2w+42w + 4 captures both operations. When 2(2w+4)2(2w + 4) is distributed during the perimeter substitution, it produces 4w+84w + 8, which then combines with 2w2w to yield a variable coefficient of 66 rather than 44. This larger coefficient is what distinguishes 'more than twice' rectangle problems from simpler additive ones.

0

1

Updated 2026-04-21

Contributors are:

Who are from:

Tags

OpenStax

Elementary Algebra @ OpenStax

Ch.3 Math Models - Elementary Algebra @ OpenStax

Algebra

Math

Prealgebra

Related
Learn After