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Finding the Fourth Proportional to 431.20, 645.63 and 257.43

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Solution

The fourth proportional to 431.20, 645.63 and 257.43 is: 385.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    431.20 : 645.63 = 257.43 : x
  2. Step 2: Convert to fraction form
    431.20/645.63 = 257.43/x
  3. Step 3: Cross multiply
    431.20x = 645.63 × 257.43
  4. Step 4: Simplify right side
    431.20x = 166,204.53
  5. Step 5: Solve for x
    x = 166,204.53/431.20
  6. Step 6: Final answer
    x = 385.45

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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.