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Finding the Fourth Proportional to 86.28, 128.90 and 79.92

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Solution

The fourth proportional to 86.28, 128.90 and 79.92 is: 119.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.28 : 128.90 = 79.92 : x
  2. Step 2: Convert to fraction form
    86.28/128.90 = 79.92/x
  3. Step 3: Cross multiply
    86.28x = 128.90 × 79.92
  4. Step 4: Simplify right side
    86.28x = 10,301.29
  5. Step 5: Solve for x
    x = 10,301.29/86.28
  6. Step 6: Final answer
    x = 119.39

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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.