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Finding the Fourth Proportional to 129.42, 178.65 and 85.74

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Solution

The fourth proportional to 129.42, 178.65 and 85.74 is: 118.35

Step by Step Solution

  1. Step 1: Write the proportion equation
    129.42 : 178.65 = 85.74 : x
  2. Step 2: Convert to fraction form
    129.42/178.65 = 85.74/x
  3. Step 3: Cross multiply
    129.42x = 178.65 × 85.74
  4. Step 4: Simplify right side
    129.42x = 15,317.45
  5. Step 5: Solve for x
    x = 15,317.45/129.42
  6. Step 6: Final answer
    x = 118.35

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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.