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Finding the Fourth Proportional to 128, 176.56 and 91.21

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Solution

The fourth proportional to 128, 176.56 and 91.21 is: 125.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    128 : 176.56 = 91.21 : x
  2. Step 2: Convert to fraction form
    128/176.56 = 91.21/x
  3. Step 3: Cross multiply
    128x = 176.56 × 91.21
  4. Step 4: Simplify right side
    128x = 16,103.15
  5. Step 5: Solve for x
    x = 16,103.15/128
  6. Step 6: Final answer
    x = 125.81

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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.