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Finding the Fourth Proportional to 81.71, 121.65 and 81.30

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Solution

The fourth proportional to 81.71, 121.65 and 81.30 is: 121.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.71 : 121.65 = 81.30 : x
  2. Step 2: Convert to fraction form
    81.71/121.65 = 81.30/x
  3. Step 3: Cross multiply
    81.71x = 121.65 × 81.30
  4. Step 4: Simplify right side
    81.71x = 9,890.15
  5. Step 5: Solve for x
    x = 9,890.15/81.71
  6. Step 6: Final answer
    x = 121.05

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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.