Home / 1,209.20-1,811.40-720.80

Finding the Fourth Proportional to 1,209.20, 1,811.40 and 720.80

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Solution

The fourth proportional to 1,209.20, 1,811.40 and 720.80 is: 1,079.77

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,209.20 : 1,811.40 = 720.80 : x
  2. Step 2: Convert to fraction form
    1,209.20/1,811.40 = 720.80/x
  3. Step 3: Cross multiply
    1,209.20x = 1,811.40 × 720.80
  4. Step 4: Simplify right side
    1,209.20x = 1,305,657.12
  5. Step 5: Solve for x
    x = 1,305,657.12/1,209.20
  6. Step 6: Final answer
    x = 1,079.77

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.