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Finding the Fourth Proportional to 813.20, 1,220.32 and 428.72

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Solution

The fourth proportional to 813.20, 1,220.32 and 428.72 is: 643.35

Step by Step Solution

  1. Step 1: Write the proportion equation
    813.20 : 1,220.32 = 428.72 : x
  2. Step 2: Convert to fraction form
    813.20/1,220.32 = 428.72/x
  3. Step 3: Cross multiply
    813.20x = 1,220.32 × 428.72
  4. Step 4: Simplify right side
    813.20x = 523,175.59
  5. Step 5: Solve for x
    x = 523,175.59/813.20
  6. Step 6: Final answer
    x = 643.35

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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.