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Finding the Fourth Proportional to 81.54, 121.64 and 71.28

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Solution

The fourth proportional to 81.54, 121.64 and 71.28 is: 106.33

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.54 : 121.64 = 71.28 : x
  2. Step 2: Convert to fraction form
    81.54/121.64 = 71.28/x
  3. Step 3: Cross multiply
    81.54x = 121.64 × 71.28
  4. Step 4: Simplify right side
    81.54x = 8,670.14
  5. Step 5: Solve for x
    x = 8,670.14/81.54
  6. Step 6: Final answer
    x = 106.33

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.