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Finding the Fourth Proportional to 428.06, 642.10 and 139.52

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Solution

The fourth proportional to 428.06, 642.10 and 139.52 is: 209.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.06 : 642.10 = 139.52 : x
  2. Step 2: Convert to fraction form
    428.06/642.10 = 139.52/x
  3. Step 3: Cross multiply
    428.06x = 642.10 × 139.52
  4. Step 4: Simplify right side
    428.06x = 89,585.79
  5. Step 5: Solve for x
    x = 89,585.79/428.06
  6. Step 6: Final answer
    x = 209.28

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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.