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Finding the Fourth Proportional to 429.20, 643.92 and 136.72

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Solution

The fourth proportional to 429.20, 643.92 and 136.72 is: 205.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    429.20 : 643.92 = 136.72 : x
  2. Step 2: Convert to fraction form
    429.20/643.92 = 136.72/x
  3. Step 3: Cross multiply
    429.20x = 643.92 × 136.72
  4. Step 4: Simplify right side
    429.20x = 88,036.74
  5. Step 5: Solve for x
    x = 88,036.74/429.20
  6. Step 6: Final answer
    x = 205.12

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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.