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Finding the Fourth Proportional to 129.42, 178.65 and 85.77

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Solution

The fourth proportional to 129.42, 178.65 and 85.77 is: 118.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    129.42 : 178.65 = 85.77 : x
  2. Step 2: Convert to fraction form
    129.42/178.65 = 85.77/x
  3. Step 3: Cross multiply
    129.42x = 178.65 × 85.77
  4. Step 4: Simplify right side
    129.42x = 15,322.81
  5. Step 5: Solve for x
    x = 15,322.81/129.42
  6. Step 6: Final answer
    x = 118.40

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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.