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Finding the Fourth Proportional to 128.66, 177.68 and 91.90

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Solution

The fourth proportional to 128.66, 177.68 and 91.90 is: 126.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.66 : 177.68 = 91.90 : x
  2. Step 2: Convert to fraction form
    128.66/177.68 = 91.90/x
  3. Step 3: Cross multiply
    128.66x = 177.68 × 91.90
  4. Step 4: Simplify right side
    128.66x = 16,328.58
  5. Step 5: Solve for x
    x = 16,328.58/128.66
  6. Step 6: Final answer
    x = 126.91

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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.