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Finding the Fourth Proportional to 686.79, 947.36 and 421.28

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Solution

The fourth proportional to 686.79, 947.36 and 421.28 is: 581.11

Step by Step Solution

  1. Step 1: Write the proportion equation
    686.79 : 947.36 = 421.28 : x
  2. Step 2: Convert to fraction form
    686.79/947.36 = 421.28/x
  3. Step 3: Cross multiply
    686.79x = 947.36 × 421.28
  4. Step 4: Simplify right side
    686.79x = 399,099.08
  5. Step 5: Solve for x
    x = 399,099.08/686.79
  6. Step 6: Final answer
    x = 581.11

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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.