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Finding the Fourth Proportional to 81, 121.32 and 71.64

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Solution

The fourth proportional to 81, 121.32 and 71.64 is: 107.30

Step by Step Solution

  1. Step 1: Write the proportion equation
    81 : 121.32 = 71.64 : x
  2. Step 2: Convert to fraction form
    81/121.32 = 71.64/x
  3. Step 3: Cross multiply
    81x = 121.32 × 71.64
  4. Step 4: Simplify right side
    81x = 8,691.36
  5. Step 5: Solve for x
    x = 8,691.36/81
  6. Step 6: Final answer
    x = 107.30

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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.