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Finding the Fourth Proportional to 86.80, 129.96 and 78.80

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Solution

The fourth proportional to 86.80, 129.96 and 78.80 is: 117.98

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.80 : 129.96 = 78.80 : x
  2. Step 2: Convert to fraction form
    86.80/129.96 = 78.80/x
  3. Step 3: Cross multiply
    86.80x = 129.96 × 78.80
  4. Step 4: Simplify right side
    86.80x = 10,240.85
  5. Step 5: Solve for x
    x = 10,240.85/86.80
  6. Step 6: Final answer
    x = 117.98

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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.