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Finding the Fourth Proportional to 103.88, 155.72 and 81.20

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Solution

The fourth proportional to 103.88, 155.72 and 81.20 is: 121.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    103.88 : 155.72 = 81.20 : x
  2. Step 2: Convert to fraction form
    103.88/155.72 = 81.20/x
  3. Step 3: Cross multiply
    103.88x = 155.72 × 81.20
  4. Step 4: Simplify right side
    103.88x = 12,645.06
  5. Step 5: Solve for x
    x = 12,645.06/103.88
  6. Step 6: Final answer
    x = 121.72

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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.