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Finding the Fourth Proportional to 821.40, 1,231.56 and 387.96

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Solution

The fourth proportional to 821.40, 1,231.56 and 387.96 is: 581.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    821.40 : 1,231.56 = 387.96 : x
  2. Step 2: Convert to fraction form
    821.40/1,231.56 = 387.96/x
  3. Step 3: Cross multiply
    821.40x = 1,231.56 × 387.96
  4. Step 4: Simplify right side
    821.40x = 477,796.02
  5. Step 5: Solve for x
    x = 477,796.02/821.40
  6. Step 6: Final answer
    x = 581.68

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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.