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Finding the Fourth Proportional to 91.74, 138.12 and 85.80

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Solution

The fourth proportional to 91.74, 138.12 and 85.80 is: 129.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.74 : 138.12 = 85.80 : x
  2. Step 2: Convert to fraction form
    91.74/138.12 = 85.80/x
  3. Step 3: Cross multiply
    91.74x = 138.12 × 85.80
  4. Step 4: Simplify right side
    91.74x = 11,850.70
  5. Step 5: Solve for x
    x = 11,850.70/91.74
  6. Step 6: Final answer
    x = 129.18

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.