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Finding the Fourth Proportional to 820.63, 1,231.55 and 387.78

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Solution

The fourth proportional to 820.63, 1,231.55 and 387.78 is: 581.96

Step by Step Solution

  1. Step 1: Write the proportion equation
    820.63 : 1,231.55 = 387.78 : x
  2. Step 2: Convert to fraction form
    820.63/1,231.55 = 387.78/x
  3. Step 3: Cross multiply
    820.63x = 1,231.55 × 387.78
  4. Step 4: Simplify right side
    820.63x = 477,568.52
  5. Step 5: Solve for x
    x = 477,568.52/820.63
  6. Step 6: Final answer
    x = 581.96

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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.