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Finding the Fourth Proportional to 91.71, 137.70 and 85.77

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Solution

The fourth proportional to 91.71, 137.70 and 85.77 is: 128.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.71 : 137.70 = 85.77 : x
  2. Step 2: Convert to fraction form
    91.71/137.70 = 85.77/x
  3. Step 3: Cross multiply
    91.71x = 137.70 × 85.77
  4. Step 4: Simplify right side
    91.71x = 11,810.53
  5. Step 5: Solve for x
    x = 11,810.53/91.71
  6. Step 6: Final answer
    x = 128.78

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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.