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Finding the Fourth Proportional to 89.91, 135 and 87.21

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Solution

The fourth proportional to 89.91, 135 and 87.21 is: 130.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    89.91 : 135 = 87.21 : x
  2. Step 2: Convert to fraction form
    89.91/135 = 87.21/x
  3. Step 3: Cross multiply
    89.91x = 135 × 87.21
  4. Step 4: Simplify right side
    89.91x = 11,773.35
  5. Step 5: Solve for x
    x = 11,773.35/89.91
  6. Step 6: Final answer
    x = 130.95

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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.