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Finding the Fourth Proportional to 280.31, 420.46 and 85.31

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Solution

The fourth proportional to 280.31, 420.46 and 85.31 is: 127.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    280.31 : 420.46 = 85.31 : x
  2. Step 2: Convert to fraction form
    280.31/420.46 = 85.31/x
  3. Step 3: Cross multiply
    280.31x = 420.46 × 85.31
  4. Step 4: Simplify right side
    280.31x = 35,867.13
  5. Step 5: Solve for x
    x = 35,867.13/280.31
  6. Step 6: Final answer
    x = 127.95

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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.