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Finding the Fourth Proportional to 128.68, 177.70 and 121.86

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Solution

The fourth proportional to 128.68, 177.70 and 121.86 is: 168.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.68 : 177.70 = 121.86 : x
  2. Step 2: Convert to fraction form
    128.68/177.70 = 121.86/x
  3. Step 3: Cross multiply
    128.68x = 177.70 × 121.86
  4. Step 4: Simplify right side
    128.68x = 21,654.52
  5. Step 5: Solve for x
    x = 21,654.52/128.68
  6. Step 6: Final answer
    x = 168.28

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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.