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Finding the Fourth Proportional to 809.78, 1,216.70 and 517.40

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Solution

The fourth proportional to 809.78, 1,216.70 and 517.40 is: 777.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    809.78 : 1,216.70 = 517.40 : x
  2. Step 2: Convert to fraction form
    809.78/1,216.70 = 517.40/x
  3. Step 3: Cross multiply
    809.78x = 1,216.70 × 517.40
  4. Step 4: Simplify right side
    809.78x = 629,520.58
  5. Step 5: Solve for x
    x = 629,520.58/809.78
  6. Step 6: Final answer
    x = 777.40

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.