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Finding the Fourth Proportional to 820.80, 1,231.55 and 431.10

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Solution

The fourth proportional to 820.80, 1,231.55 and 431.10 is: 646.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    820.80 : 1,231.55 = 431.10 : x
  2. Step 2: Convert to fraction form
    820.80/1,231.55 = 431.10/x
  3. Step 3: Cross multiply
    820.80x = 1,231.55 × 431.10
  4. Step 4: Simplify right side
    820.80x = 530,921.21
  5. Step 5: Solve for x
    x = 530,921.21/820.80
  6. Step 6: Final answer
    x = 646.83

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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.