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Finding the Fourth Proportional to 86.43, 128.98 and 77.32

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Solution

The fourth proportional to 86.43, 128.98 and 77.32 is: 115.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.43 : 128.98 = 77.32 : x
  2. Step 2: Convert to fraction form
    86.43/128.98 = 77.32/x
  3. Step 3: Cross multiply
    86.43x = 128.98 × 77.32
  4. Step 4: Simplify right side
    86.43x = 9,972.73
  5. Step 5: Solve for x
    x = 9,972.73/86.43
  6. Step 6: Final answer
    x = 115.39

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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.