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Finding the Fourth Proportional to 428.45, 642.72 and 139.94

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Solution

The fourth proportional to 428.45, 642.72 and 139.94 is: 209.93

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.45 : 642.72 = 139.94 : x
  2. Step 2: Convert to fraction form
    428.45/642.72 = 139.94/x
  3. Step 3: Cross multiply
    428.45x = 642.72 × 139.94
  4. Step 4: Simplify right side
    428.45x = 89,944.37
  5. Step 5: Solve for x
    x = 89,944.37/428.45
  6. Step 6: Final answer
    x = 209.93

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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.