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Finding the Fourth Proportional to 86.28, 128.79 and 71.64

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Solution

The fourth proportional to 86.28, 128.79 and 71.64 is: 106.94

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.28 : 128.79 = 71.64 : x
  2. Step 2: Convert to fraction form
    86.28/128.79 = 71.64/x
  3. Step 3: Cross multiply
    86.28x = 128.79 × 71.64
  4. Step 4: Simplify right side
    86.28x = 9,226.52
  5. Step 5: Solve for x
    x = 9,226.52/86.28
  6. Step 6: Final answer
    x = 106.94

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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.