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Finding the Fourth Proportional to 428.29, 642.57 and 139.66

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Solution

The fourth proportional to 428.29, 642.57 and 139.66 is: 209.53

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.29 : 642.57 = 139.66 : x
  2. Step 2: Convert to fraction form
    428.29/642.57 = 139.66/x
  3. Step 3: Cross multiply
    428.29x = 642.57 × 139.66
  4. Step 4: Simplify right side
    428.29x = 89,741.33
  5. Step 5: Solve for x
    x = 89,741.33/428.29
  6. Step 6: Final answer
    x = 209.53

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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.