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Finding the Fourth Proportional to 821.78, 1,229.70 and 513.80

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Solution

The fourth proportional to 821.78, 1,229.70 and 513.80 is: 768.84

Step by Step Solution

  1. Step 1: Write the proportion equation
    821.78 : 1,229.70 = 513.80 : x
  2. Step 2: Convert to fraction form
    821.78/1,229.70 = 513.80/x
  3. Step 3: Cross multiply
    821.78x = 1,229.70 × 513.80
  4. Step 4: Simplify right side
    821.78x = 631,819.86
  5. Step 5: Solve for x
    x = 631,819.86/821.78
  6. Step 6: Final answer
    x = 768.84

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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.