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Finding the Fourth Proportional to 128.21, 176.91 and 81.57

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Solution

The fourth proportional to 128.21, 176.91 and 81.57 is: 112.56

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.21 : 176.91 = 81.57 : x
  2. Step 2: Convert to fraction form
    128.21/176.91 = 81.57/x
  3. Step 3: Cross multiply
    128.21x = 176.91 × 81.57
  4. Step 4: Simplify right side
    128.21x = 14,430.55
  5. Step 5: Solve for x
    x = 14,430.55/128.21
  6. Step 6: Final answer
    x = 112.56

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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.