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Finding the Fourth Proportional to 128.11, 176.86 and 90.31

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Solution

The fourth proportional to 128.11, 176.86 and 90.31 is: 124.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.11 : 176.86 = 90.31 : x
  2. Step 2: Convert to fraction form
    128.11/176.86 = 90.31/x
  3. Step 3: Cross multiply
    128.11x = 176.86 × 90.31
  4. Step 4: Simplify right side
    128.11x = 15,971.78
  5. Step 5: Solve for x
    x = 15,971.78/128.11
  6. Step 6: Final answer
    x = 124.68

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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.