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Finding the Fourth Proportional to 91.78, 126.88 and 81.38

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Solution

The fourth proportional to 91.78, 126.88 and 81.38 is: 112.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.78 : 126.88 = 81.38 : x
  2. Step 2: Convert to fraction form
    91.78/126.88 = 81.38/x
  3. Step 3: Cross multiply
    91.78x = 126.88 × 81.38
  4. Step 4: Simplify right side
    91.78x = 10,325.49
  5. Step 5: Solve for x
    x = 10,325.49/91.78
  6. Step 6: Final answer
    x = 112.50

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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.