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Finding the Fourth Proportional to 781.20, 1,078.42 and 486.65

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Solution

The fourth proportional to 781.20, 1,078.42 and 486.65 is: 671.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.20 : 1,078.42 = 486.65 : x
  2. Step 2: Convert to fraction form
    781.20/1,078.42 = 486.65/x
  3. Step 3: Cross multiply
    781.20x = 1,078.42 × 486.65
  4. Step 4: Simplify right side
    781.20x = 524,813.09
  5. Step 5: Solve for x
    x = 524,813.09/781.20
  6. Step 6: Final answer
    x = 671.80

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.