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Finding the Fourth Proportional to 81.40, 122.10 and 66.11

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Solution

The fourth proportional to 81.40, 122.10 and 66.11 is: 99.17

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.40 : 122.10 = 66.11 : x
  2. Step 2: Convert to fraction form
    81.40/122.10 = 66.11/x
  3. Step 3: Cross multiply
    81.40x = 122.10 × 66.11
  4. Step 4: Simplify right side
    81.40x = 8,072.03
  5. Step 5: Solve for x
    x = 8,072.03/81.40
  6. Step 6: Final answer
    x = 99.17

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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.