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Finding the Fourth Proportional to 91.80, 137.42 and 85.88

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Solution

The fourth proportional to 91.80, 137.42 and 85.88 is: 128.56

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.80 : 137.42 = 85.88 : x
  2. Step 2: Convert to fraction form
    91.80/137.42 = 85.88/x
  3. Step 3: Cross multiply
    91.80x = 137.42 × 85.88
  4. Step 4: Simplify right side
    91.80x = 11,801.63
  5. Step 5: Solve for x
    x = 11,801.63/91.80
  6. Step 6: Final answer
    x = 128.56

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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.