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Finding the Fourth Proportional to 81.30, 121.87 and 42.80

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Solution

The fourth proportional to 81.30, 121.87 and 42.80 is: 64.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.30 : 121.87 = 42.80 : x
  2. Step 2: Convert to fraction form
    81.30/121.87 = 42.80/x
  3. Step 3: Cross multiply
    81.30x = 121.87 × 42.80
  4. Step 4: Simplify right side
    81.30x = 5,215.48
  5. Step 5: Solve for x
    x = 5,215.48/81.30
  6. Step 6: Final answer
    x = 64.15

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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.