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Finding the Fourth Proportional to 86.65, 129.99 and 31.81

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Solution

The fourth proportional to 86.65, 129.99 and 31.81 is: 47.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.65 : 129.99 = 31.81 : x
  2. Step 2: Convert to fraction form
    86.65/129.99 = 31.81/x
  3. Step 3: Cross multiply
    86.65x = 129.99 × 31.81
  4. Step 4: Simplify right side
    86.65x = 4,134.98
  5. Step 5: Solve for x
    x = 4,134.98/86.65
  6. Step 6: Final answer
    x = 47.72

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.