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Finding the Fourth Proportional to 211.80, 292.20 and 128.86

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Solution

The fourth proportional to 211.80, 292.20 and 128.86 is: 177.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    211.80 : 292.20 = 128.86 : x
  2. Step 2: Convert to fraction form
    211.80/292.20 = 128.86/x
  3. Step 3: Cross multiply
    211.80x = 292.20 × 128.86
  4. Step 4: Simplify right side
    211.80x = 37,652.89
  5. Step 5: Solve for x
    x = 37,652.89/211.80
  6. Step 6: Final answer
    x = 177.78

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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.