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Finding the Fourth Proportional to 769.92, 1,155.68 and 428.16

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Solution

The fourth proportional to 769.92, 1,155.68 and 428.16 is: 642.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    769.92 : 1,155.68 = 428.16 : x
  2. Step 2: Convert to fraction form
    769.92/1,155.68 = 428.16/x
  3. Step 3: Cross multiply
    769.92x = 1,155.68 × 428.16
  4. Step 4: Simplify right side
    769.92x = 494,815.95
  5. Step 5: Solve for x
    x = 494,815.95/769.92
  6. Step 6: Final answer
    x = 642.68

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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.