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Finding the Fourth Proportional to 311.20, 428.40 and 283.12

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Solution

The fourth proportional to 311.20, 428.40 and 283.12 is: 389.74

Step by Step Solution

  1. Step 1: Write the proportion equation
    311.20 : 428.40 = 283.12 : x
  2. Step 2: Convert to fraction form
    311.20/428.40 = 283.12/x
  3. Step 3: Cross multiply
    311.20x = 428.40 × 283.12
  4. Step 4: Simplify right side
    311.20x = 121,288.61
  5. Step 5: Solve for x
    x = 121,288.61/311.20
  6. Step 6: Final answer
    x = 389.74

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.