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Finding the Fourth Proportional to 128.90, 193.11 and 86.18

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Solution

The fourth proportional to 128.90, 193.11 and 86.18 is: 129.11

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.90 : 193.11 = 86.18 : x
  2. Step 2: Convert to fraction form
    128.90/193.11 = 86.18/x
  3. Step 3: Cross multiply
    128.90x = 193.11 × 86.18
  4. Step 4: Simplify right side
    128.90x = 16,642.22
  5. Step 5: Solve for x
    x = 16,642.22/128.90
  6. Step 6: Final answer
    x = 129.11

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.