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Finding the Fourth Proportional to 421.12, 628.61 and 390.28

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Solution

The fourth proportional to 421.12, 628.61 and 390.28 is: 582.57

Step by Step Solution

  1. Step 1: Write the proportion equation
    421.12 : 628.61 = 390.28 : x
  2. Step 2: Convert to fraction form
    421.12/628.61 = 390.28/x
  3. Step 3: Cross multiply
    421.12x = 628.61 × 390.28
  4. Step 4: Simplify right side
    421.12x = 245,333.91
  5. Step 5: Solve for x
    x = 245,333.91/421.12
  6. Step 6: Final answer
    x = 582.57

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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.