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Finding the Fourth Proportional to 129.40, 178.68 and 90.64

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Solution

The fourth proportional to 129.40, 178.68 and 90.64 is: 125.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    129.40 : 178.68 = 90.64 : x
  2. Step 2: Convert to fraction form
    129.40/178.68 = 90.64/x
  3. Step 3: Cross multiply
    129.40x = 178.68 × 90.64
  4. Step 4: Simplify right side
    129.40x = 16,195.56
  5. Step 5: Solve for x
    x = 16,195.56/129.40
  6. Step 6: Final answer
    x = 125.16

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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.