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Finding the Fourth Proportional to 708.40, 978.60 and 686.80

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Solution

The fourth proportional to 708.40, 978.60 and 686.80 is: 948.76

Step by Step Solution

  1. Step 1: Write the proportion equation
    708.40 : 978.60 = 686.80 : x
  2. Step 2: Convert to fraction form
    708.40/978.60 = 686.80/x
  3. Step 3: Cross multiply
    708.40x = 978.60 × 686.80
  4. Step 4: Simplify right side
    708.40x = 672,102.48
  5. Step 5: Solve for x
    x = 672,102.48/708.40
  6. Step 6: Final answer
    x = 948.76

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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.