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Finding the Fourth Proportional to 100.28, 138.32 and 65.78

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Solution

The fourth proportional to 100.28, 138.32 and 65.78 is: 90.73

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.28 : 138.32 = 65.78 : x
  2. Step 2: Convert to fraction form
    100.28/138.32 = 65.78/x
  3. Step 3: Cross multiply
    100.28x = 138.32 × 65.78
  4. Step 4: Simplify right side
    100.28x = 9,098.69
  5. Step 5: Solve for x
    x = 9,098.69/100.28
  6. Step 6: Final answer
    x = 90.73

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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.