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Finding the Fourth Proportional to 813.24, 1,220.40 and 428.76

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Solution

The fourth proportional to 813.24, 1,220.40 and 428.76 is: 643.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    813.24 : 1,220.40 = 428.76 : x
  2. Step 2: Convert to fraction form
    813.24/1,220.40 = 428.76/x
  3. Step 3: Cross multiply
    813.24x = 1,220.40 × 428.76
  4. Step 4: Simplify right side
    813.24x = 523,258.70
  5. Step 5: Solve for x
    x = 523,258.70/813.24
  6. Step 6: Final answer
    x = 643.42

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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.