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Finding the Fourth Proportional to 81.12, 121.07 and 72

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Solution

The fourth proportional to 81.12, 121.07 and 72 is: 107.46

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.12 : 121.07 = 72 : x
  2. Step 2: Convert to fraction form
    81.12/121.07 = 72/x
  3. Step 3: Cross multiply
    81.12x = 121.07 × 72
  4. Step 4: Simplify right side
    81.12x = 8,717.04
  5. Step 5: Solve for x
    x = 8,717.04/81.12
  6. Step 6: Final answer
    x = 107.46

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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.