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Finding the Fourth Proportional to 86.76, 129.66 and 86.16

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Solution

The fourth proportional to 86.76, 129.66 and 86.16 is: 128.76

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.76 : 129.66 = 86.16 : x
  2. Step 2: Convert to fraction form
    86.76/129.66 = 86.16/x
  3. Step 3: Cross multiply
    86.76x = 129.66 × 86.16
  4. Step 4: Simplify right side
    86.76x = 11,171.51
  5. Step 5: Solve for x
    x = 11,171.51/86.76
  6. Step 6: Final answer
    x = 128.76

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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.