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Finding the Fourth Proportional to 211.55, 291.89 and 128.75

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Solution

The fourth proportional to 211.55, 291.89 and 128.75 is: 177.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    211.55 : 291.89 = 128.75 : x
  2. Step 2: Convert to fraction form
    211.55/291.89 = 128.75/x
  3. Step 3: Cross multiply
    211.55x = 291.89 × 128.75
  4. Step 4: Simplify right side
    211.55x = 37,579.70
  5. Step 5: Solve for x
    x = 37,579.70/211.55
  6. Step 6: Final answer
    x = 177.64

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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.