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Finding the Fourth Proportional to 129.78, 194.45 and 78.21

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Solution

The fourth proportional to 129.78, 194.45 and 78.21 is: 117.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    129.78 : 194.45 = 78.21 : x
  2. Step 2: Convert to fraction form
    129.78/194.45 = 78.21/x
  3. Step 3: Cross multiply
    129.78x = 194.45 × 78.21
  4. Step 4: Simplify right side
    129.78x = 15,207.54
  5. Step 5: Solve for x
    x = 15,207.54/129.78
  6. Step 6: Final answer
    x = 117.18

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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.