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Finding the Fourth Proportional to 431.76, 643.49 and 431.09

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Solution

The fourth proportional to 431.76, 643.49 and 431.09 is: 642.48

Step by Step Solution

  1. Step 1: Write the proportion equation
    431.76 : 643.49 = 431.09 : x
  2. Step 2: Convert to fraction form
    431.76/643.49 = 431.09/x
  3. Step 3: Cross multiply
    431.76x = 643.49 × 431.09
  4. Step 4: Simplify right side
    431.76x = 277,396.73
  5. Step 5: Solve for x
    x = 277,396.73/431.76
  6. Step 6: Final answer
    x = 642.48

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.