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Finding the Fourth Proportional to 86.49, 129.05 and 78.39

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Solution

The fourth proportional to 86.49, 129.05 and 78.39 is: 116.96

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.49 : 129.05 = 78.39 : x
  2. Step 2: Convert to fraction form
    86.49/129.05 = 78.39/x
  3. Step 3: Cross multiply
    86.49x = 129.05 × 78.39
  4. Step 4: Simplify right side
    86.49x = 10,115.84
  5. Step 5: Solve for x
    x = 10,115.84/86.49
  6. Step 6: Final answer
    x = 116.96

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.