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Finding the Fourth Proportional to 686.90, 947.94 and 421.31

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Solution

The fourth proportional to 686.90, 947.94 and 421.31 is: 581.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    686.90 : 947.94 = 421.31 : x
  2. Step 2: Convert to fraction form
    686.90/947.94 = 421.31/x
  3. Step 3: Cross multiply
    686.90x = 947.94 × 421.31
  4. Step 4: Simplify right side
    686.90x = 399,376.60
  5. Step 5: Solve for x
    x = 399,376.60/686.90
  6. Step 6: Final answer
    x = 581.42

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.