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Finding the Fourth Proportional to 86.72, 130.20 and 85.28

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Solution

The fourth proportional to 86.72, 130.20 and 85.28 is: 128.04

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.72 : 130.20 = 85.28 : x
  2. Step 2: Convert to fraction form
    86.72/130.20 = 85.28/x
  3. Step 3: Cross multiply
    86.72x = 130.20 × 85.28
  4. Step 4: Simplify right side
    86.72x = 11,103.46
  5. Step 5: Solve for x
    x = 11,103.46/86.72
  6. Step 6: Final answer
    x = 128.04

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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.