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Finding the Fourth Proportional to 91.29, 126 and 78.21

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Solution

The fourth proportional to 91.29, 126 and 78.21 is: 107.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.29 : 126 = 78.21 : x
  2. Step 2: Convert to fraction form
    91.29/126 = 78.21/x
  3. Step 3: Cross multiply
    91.29x = 126 × 78.21
  4. Step 4: Simplify right side
    91.29x = 9,854.46
  5. Step 5: Solve for x
    x = 9,854.46/91.29
  6. Step 6: Final answer
    x = 107.95

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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.