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Finding the Fourth Proportional to 90.32, 135.20 and 81.28

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Solution

The fourth proportional to 90.32, 135.20 and 81.28 is: 121.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.32 : 135.20 = 81.28 : x
  2. Step 2: Convert to fraction form
    90.32/135.20 = 81.28/x
  3. Step 3: Cross multiply
    90.32x = 135.20 × 81.28
  4. Step 4: Simplify right side
    90.32x = 10,989.06
  5. Step 5: Solve for x
    x = 10,989.06/90.32
  6. Step 6: Final answer
    x = 121.67

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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.