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Finding the Fourth Proportional to 90.72, 125.28 and 81.12

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Solution

The fourth proportional to 90.72, 125.28 and 81.12 is: 112.02

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.72 : 125.28 = 81.12 : x
  2. Step 2: Convert to fraction form
    90.72/125.28 = 81.12/x
  3. Step 3: Cross multiply
    90.72x = 125.28 × 81.12
  4. Step 4: Simplify right side
    90.72x = 10,162.71
  5. Step 5: Solve for x
    x = 10,162.71/90.72
  6. Step 6: Final answer
    x = 112.02

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.