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Finding the Fourth Proportional to 129.40, 178.42 and 85.64

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Solution

The fourth proportional to 129.40, 178.42 and 85.64 is: 118.08

Step by Step Solution

  1. Step 1: Write the proportion equation
    129.40 : 178.42 = 85.64 : x
  2. Step 2: Convert to fraction form
    129.40/178.42 = 85.64/x
  3. Step 3: Cross multiply
    129.40x = 178.42 × 85.64
  4. Step 4: Simplify right side
    129.40x = 15,279.89
  5. Step 5: Solve for x
    x = 15,279.89/129.40
  6. Step 6: Final answer
    x = 118.08

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.