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Finding the Fourth Proportional to 781.60, 1,078.20 and 487.12

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Solution

The fourth proportional to 781.60, 1,078.20 and 487.12 is: 671.97

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.60 : 1,078.20 = 487.12 : x
  2. Step 2: Convert to fraction form
    781.60/1,078.20 = 487.12/x
  3. Step 3: Cross multiply
    781.60x = 1,078.20 × 487.12
  4. Step 4: Simplify right side
    781.60x = 525,212.78
  5. Step 5: Solve for x
    x = 525,212.78/781.60
  6. Step 6: Final answer
    x = 671.97

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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.