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Finding the Fourth Proportional to 820.90, 1,231.28 and 243.78

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Solution

The fourth proportional to 820.90, 1,231.28 and 243.78 is: 365.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    820.90 : 1,231.28 = 243.78 : x
  2. Step 2: Convert to fraction form
    820.90/1,231.28 = 243.78/x
  3. Step 3: Cross multiply
    820.90x = 1,231.28 × 243.78
  4. Step 4: Simplify right side
    820.90x = 300,161.44
  5. Step 5: Solve for x
    x = 300,161.44/820.90
  6. Step 6: Final answer
    x = 365.65

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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.