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Finding the Fourth Proportional to 428, 641.92 and 139.44

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Solution

The fourth proportional to 428, 641.92 and 139.44 is: 209.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    428 : 641.92 = 139.44 : x
  2. Step 2: Convert to fraction form
    428/641.92 = 139.44/x
  3. Step 3: Cross multiply
    428x = 641.92 × 139.44
  4. Step 4: Simplify right side
    428x = 89,509.32
  5. Step 5: Solve for x
    x = 89,509.32/428
  6. Step 6: Final answer
    x = 209.13

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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.