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Finding the Fourth Proportional to 785.78, 1,178.65 and 421.28

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Solution

The fourth proportional to 785.78, 1,178.65 and 421.28 is: 631.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    785.78 : 1,178.65 = 421.28 : x
  2. Step 2: Convert to fraction form
    785.78/1,178.65 = 421.28/x
  3. Step 3: Cross multiply
    785.78x = 1,178.65 × 421.28
  4. Step 4: Simplify right side
    785.78x = 496,540.73
  5. Step 5: Solve for x
    x = 496,540.73/785.78
  6. Step 6: Final answer
    x = 631.91

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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.