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Finding the Fourth Proportional to 86.81, 130.20 and 31.21

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Solution

The fourth proportional to 86.81, 130.20 and 31.21 is: 46.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.81 : 130.20 = 31.21 : x
  2. Step 2: Convert to fraction form
    86.81/130.20 = 31.21/x
  3. Step 3: Cross multiply
    86.81x = 130.20 × 31.21
  4. Step 4: Simplify right side
    86.81x = 4,063.28
  5. Step 5: Solve for x
    x = 4,063.28/86.81
  6. Step 6: Final answer
    x = 46.81

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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.