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Finding the Fourth Proportional to 138.40, 190.94 and 91.78

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Solution

The fourth proportional to 138.40, 190.94 and 91.78 is: 126.62

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.40 : 190.94 = 91.78 : x
  2. Step 2: Convert to fraction form
    138.40/190.94 = 91.78/x
  3. Step 3: Cross multiply
    138.40x = 190.94 × 91.78
  4. Step 4: Simplify right side
    138.40x = 17,523.54
  5. Step 5: Solve for x
    x = 17,523.54/138.40
  6. Step 6: Final answer
    x = 126.62

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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.