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Finding the Fourth Proportional to 86.94, 129.48 and 81.71

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Solution

The fourth proportional to 86.94, 129.48 and 81.71 is: 121.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.94 : 129.48 = 81.71 : x
  2. Step 2: Convert to fraction form
    86.94/129.48 = 81.71/x
  3. Step 3: Cross multiply
    86.94x = 129.48 × 81.71
  4. Step 4: Simplify right side
    86.94x = 10,579.34
  5. Step 5: Solve for x
    x = 10,579.34/86.94
  6. Step 6: Final answer
    x = 121.69

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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.