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Finding the Fourth Proportional to 81.51, 121.35 and 81.11

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Solution

The fourth proportional to 81.51, 121.35 and 81.11 is: 120.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.51 : 121.35 = 81.11 : x
  2. Step 2: Convert to fraction form
    81.51/121.35 = 81.11/x
  3. Step 3: Cross multiply
    81.51x = 121.35 × 81.11
  4. Step 4: Simplify right side
    81.51x = 9,842.09
  5. Step 5: Solve for x
    x = 9,842.09/81.51
  6. Step 6: Final answer
    x = 120.75

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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.