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Finding the Fourth Proportional to 820.78, 1,228.20 and 512.80

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Solution

The fourth proportional to 820.78, 1,228.20 and 512.80 is: 767.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    820.78 : 1,228.20 = 512.80 : x
  2. Step 2: Convert to fraction form
    820.78/1,228.20 = 512.80/x
  3. Step 3: Cross multiply
    820.78x = 1,228.20 × 512.80
  4. Step 4: Simplify right side
    820.78x = 629,820.96
  5. Step 5: Solve for x
    x = 629,820.96/820.78
  6. Step 6: Final answer
    x = 767.34

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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.