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Finding the Fourth Proportional to 103.68, 142.72 and 81.76

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Solution

The fourth proportional to 103.68, 142.72 and 81.76 is: 112.55

Step by Step Solution

  1. Step 1: Write the proportion equation
    103.68 : 142.72 = 81.76 : x
  2. Step 2: Convert to fraction form
    103.68/142.72 = 81.76/x
  3. Step 3: Cross multiply
    103.68x = 142.72 × 81.76
  4. Step 4: Simplify right side
    103.68x = 11,668.79
  5. Step 5: Solve for x
    x = 11,668.79/103.68
  6. Step 6: Final answer
    x = 112.55

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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.