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Finding the Fourth Proportional to 91.47, 137.21 and 78.61

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Solution

The fourth proportional to 91.47, 137.21 and 78.61 is: 117.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.47 : 137.21 = 78.61 : x
  2. Step 2: Convert to fraction form
    91.47/137.21 = 78.61/x
  3. Step 3: Cross multiply
    91.47x = 137.21 × 78.61
  4. Step 4: Simplify right side
    91.47x = 10,786.08
  5. Step 5: Solve for x
    x = 10,786.08/91.47
  6. Step 6: Final answer
    x = 117.92

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.