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Finding the Fourth Proportional to 920.15, 1,378.39 and 431.72

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Solution

The fourth proportional to 920.15, 1,378.39 and 431.72 is: 646.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    920.15 : 1,378.39 = 431.72 : x
  2. Step 2: Convert to fraction form
    920.15/1,378.39 = 431.72/x
  3. Step 3: Cross multiply
    920.15x = 1,378.39 × 431.72
  4. Step 4: Simplify right side
    920.15x = 595,078.53
  5. Step 5: Solve for x
    x = 595,078.53/920.15
  6. Step 6: Final answer
    x = 646.72

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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.