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Finding the Fourth Proportional to 421.39, 631.21 and 390.63

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Solution

The fourth proportional to 421.39, 631.21 and 390.63 is: 585.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    421.39 : 631.21 = 390.63 : x
  2. Step 2: Convert to fraction form
    421.39/631.21 = 390.63/x
  3. Step 3: Cross multiply
    421.39x = 631.21 × 390.63
  4. Step 4: Simplify right side
    421.39x = 246,569.56
  5. Step 5: Solve for x
    x = 246,569.56/421.39
  6. Step 6: Final answer
    x = 585.13

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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.