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Finding the Fourth Proportional to 86.67, 129.33 and 72.90

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Solution

The fourth proportional to 86.67, 129.33 and 72.90 is: 108.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.67 : 129.33 = 72.90 : x
  2. Step 2: Convert to fraction form
    86.67/129.33 = 72.90/x
  3. Step 3: Cross multiply
    86.67x = 129.33 × 72.90
  4. Step 4: Simplify right side
    86.67x = 9,428.16
  5. Step 5: Solve for x
    x = 9,428.16/86.67
  6. Step 6: Final answer
    x = 108.78

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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.