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Finding the Fourth Proportional to 91.21, 136.70 and 71.87

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Solution

The fourth proportional to 91.21, 136.70 and 71.87 is: 107.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.21 : 136.70 = 71.87 : x
  2. Step 2: Convert to fraction form
    91.21/136.70 = 71.87/x
  3. Step 3: Cross multiply
    91.21x = 136.70 × 71.87
  4. Step 4: Simplify right side
    91.21x = 9,824.75
  5. Step 5: Solve for x
    x = 9,824.75/91.21
  6. Step 6: Final answer
    x = 107.72

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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.