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Finding the Fourth Proportional to 86.64, 129.28 and 85.72

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Solution

The fourth proportional to 86.64, 129.28 and 85.72 is: 127.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.64 : 129.28 = 85.72 : x
  2. Step 2: Convert to fraction form
    86.64/129.28 = 85.72/x
  3. Step 3: Cross multiply
    86.64x = 129.28 × 85.72
  4. Step 4: Simplify right side
    86.64x = 11,081.88
  5. Step 5: Solve for x
    x = 11,081.88/86.64
  6. Step 6: Final answer
    x = 127.91

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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.