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Finding the Fourth Proportional to 86.34, 128.99 and 81.90

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Solution

The fourth proportional to 86.34, 128.99 and 81.90 is: 122.36

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.34 : 128.99 = 81.90 : x
  2. Step 2: Convert to fraction form
    86.34/128.99 = 81.90/x
  3. Step 3: Cross multiply
    86.34x = 128.99 × 81.90
  4. Step 4: Simplify right side
    86.34x = 10,564.28
  5. Step 5: Solve for x
    x = 10,564.28/86.34
  6. Step 6: Final answer
    x = 122.36

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.