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Finding the Fourth Proportional to 90.71, 135.21 and 86.69

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Solution

The fourth proportional to 90.71, 135.21 and 86.69 is: 129.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.71 : 135.21 = 86.69 : x
  2. Step 2: Convert to fraction form
    90.71/135.21 = 86.69/x
  3. Step 3: Cross multiply
    90.71x = 135.21 × 86.69
  4. Step 4: Simplify right side
    90.71x = 11,721.35
  5. Step 5: Solve for x
    x = 11,721.35/90.71
  6. Step 6: Final answer
    x = 129.22

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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.