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Finding the Fourth Proportional to 686.78, 947.76 and 407.15

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Solution

The fourth proportional to 686.78, 947.76 and 407.15 is: 561.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    686.78 : 947.76 = 407.15 : x
  2. Step 2: Convert to fraction form
    686.78/947.76 = 407.15/x
  3. Step 3: Cross multiply
    686.78x = 947.76 × 407.15
  4. Step 4: Simplify right side
    686.78x = 385,882.85
  5. Step 5: Solve for x
    x = 385,882.85/686.78
  6. Step 6: Final answer
    x = 561.87

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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.