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Finding the Fourth Proportional to 129.51, 178.70 and 120.78

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Solution

The fourth proportional to 129.51, 178.70 and 120.78 is: 166.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    129.51 : 178.70 = 120.78 : x
  2. Step 2: Convert to fraction form
    129.51/178.70 = 120.78/x
  3. Step 3: Cross multiply
    129.51x = 178.70 × 120.78
  4. Step 4: Simplify right side
    129.51x = 21,582.78
  5. Step 5: Solve for x
    x = 21,582.78/129.51
  6. Step 6: Final answer
    x = 166.65

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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.