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Finding the Fourth Proportional to 86.32, 129.20 and 78.11

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Solution

The fourth proportional to 86.32, 129.20 and 78.11 is: 116.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.32 : 129.20 = 78.11 : x
  2. Step 2: Convert to fraction form
    86.32/129.20 = 78.11/x
  3. Step 3: Cross multiply
    86.32x = 129.20 × 78.11
  4. Step 4: Simplify right side
    86.32x = 10,091.74
  5. Step 5: Solve for x
    x = 10,091.74/86.32
  6. Step 6: Final answer
    x = 116.91

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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.