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Finding the Fourth Proportional to 86.90, 129.72 and 80.82

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Solution

The fourth proportional to 86.90, 129.72 and 80.82 is: 120.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.90 : 129.72 = 80.82 : x
  2. Step 2: Convert to fraction form
    86.90/129.72 = 80.82/x
  3. Step 3: Cross multiply
    86.90x = 129.72 × 80.82
  4. Step 4: Simplify right side
    86.90x = 10,483.97
  5. Step 5: Solve for x
    x = 10,483.97/86.90
  6. Step 6: Final answer
    x = 120.65

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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.