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Finding the Fourth Proportional to 821.40, 1,231.20 and 474.90

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Solution

The fourth proportional to 821.40, 1,231.20 and 474.90 is: 711.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    821.40 : 1,231.20 = 474.90 : x
  2. Step 2: Convert to fraction form
    821.40/1,231.20 = 474.90/x
  3. Step 3: Cross multiply
    821.40x = 1,231.20 × 474.90
  4. Step 4: Simplify right side
    821.40x = 584,696.88
  5. Step 5: Solve for x
    x = 584,696.88/821.40
  6. Step 6: Final answer
    x = 711.83

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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.