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Finding the Fourth Proportional to 86.40, 129.62 and 77.90

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Solution

The fourth proportional to 86.40, 129.62 and 77.90 is: 116.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.40 : 129.62 = 77.90 : x
  2. Step 2: Convert to fraction form
    86.40/129.62 = 77.90/x
  3. Step 3: Cross multiply
    86.40x = 129.62 × 77.90
  4. Step 4: Simplify right side
    86.40x = 10,096.94
  5. Step 5: Solve for x
    x = 10,096.94/86.40
  6. Step 6: Final answer
    x = 116.86

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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.