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Finding the Fourth Proportional to 81, 120.96 and 71.28

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Solution

The fourth proportional to 81, 120.96 and 71.28 is: 106.44

Step by Step Solution

  1. Step 1: Write the proportion equation
    81 : 120.96 = 71.28 : x
  2. Step 2: Convert to fraction form
    81/120.96 = 71.28/x
  3. Step 3: Cross multiply
    81x = 120.96 × 71.28
  4. Step 4: Simplify right side
    81x = 8,622.03
  5. Step 5: Solve for x
    x = 8,622.03/81
  6. Step 6: Final answer
    x = 106.44

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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.