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Finding the Fourth Proportional to 520.80, 780.40 and 439.20

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Solution

The fourth proportional to 520.80, 780.40 and 439.20 is: 658.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    520.80 : 780.40 = 439.20 : x
  2. Step 2: Convert to fraction form
    520.80/780.40 = 439.20/x
  3. Step 3: Cross multiply
    520.80x = 780.40 × 439.20
  4. Step 4: Simplify right side
    520.80x = 342,751.68
  5. Step 5: Solve for x
    x = 342,751.68/520.80
  6. Step 6: Final answer
    x = 658.13

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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.