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Finding the Fourth Proportional to 421.20, 631.80 and 385.56

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Solution

The fourth proportional to 421.20, 631.80 and 385.56 is: 578.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    421.20 : 631.80 = 385.56 : x
  2. Step 2: Convert to fraction form
    421.20/631.80 = 385.56/x
  3. Step 3: Cross multiply
    421.20x = 631.80 × 385.56
  4. Step 4: Simplify right side
    421.20x = 243,596.81
  5. Step 5: Solve for x
    x = 243,596.81/421.20
  6. Step 6: Final answer
    x = 578.34

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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.