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Finding the Fourth Proportional to 91.42, 138.12 and 90.61

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Solution

The fourth proportional to 91.42, 138.12 and 90.61 is: 136.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.42 : 138.12 = 90.61 : x
  2. Step 2: Convert to fraction form
    91.42/138.12 = 90.61/x
  3. Step 3: Cross multiply
    91.42x = 138.12 × 90.61
  4. Step 4: Simplify right side
    91.42x = 12,515.57
  5. Step 5: Solve for x
    x = 12,515.57/91.42
  6. Step 6: Final answer
    x = 136.90

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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.