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Finding the Fourth Proportional to 428.14, 642.12 and 139.60

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Solution

The fourth proportional to 428.14, 642.12 and 139.60 is: 209.37

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.14 : 642.12 = 139.60 : x
  2. Step 2: Convert to fraction form
    428.14/642.12 = 139.60/x
  3. Step 3: Cross multiply
    428.14x = 642.12 × 139.60
  4. Step 4: Simplify right side
    428.14x = 89,639.95
  5. Step 5: Solve for x
    x = 89,639.95/428.14
  6. Step 6: Final answer
    x = 209.37

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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.