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Finding the Fourth Proportional to 720.12, 1,078.16 and 389.87

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Solution

The fourth proportional to 720.12, 1,078.16 and 389.87 is: 583.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    720.12 : 1,078.16 = 389.87 : x
  2. Step 2: Convert to fraction form
    720.12/1,078.16 = 389.87/x
  3. Step 3: Cross multiply
    720.12x = 1,078.16 × 389.87
  4. Step 4: Simplify right side
    720.12x = 420,345.91
  5. Step 5: Solve for x
    x = 420,345.91/720.12
  6. Step 6: Final answer
    x = 583.72

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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.