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Finding the Fourth Proportional to 86.20, 129.15 and 57.21

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Solution

The fourth proportional to 86.20, 129.15 and 57.21 is: 85.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.20 : 129.15 = 57.21 : x
  2. Step 2: Convert to fraction form
    86.20/129.15 = 57.21/x
  3. Step 3: Cross multiply
    86.20x = 129.15 × 57.21
  4. Step 4: Simplify right side
    86.20x = 7,388.67
  5. Step 5: Solve for x
    x = 7,388.67/86.20
  6. Step 6: Final answer
    x = 85.72

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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.