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Finding the Fourth Proportional to 211.29, 291.61 and 128.40

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Solution

The fourth proportional to 211.29, 291.61 and 128.40 is: 177.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    211.29 : 291.61 = 128.40 : x
  2. Step 2: Convert to fraction form
    211.29/291.61 = 128.40/x
  3. Step 3: Cross multiply
    211.29x = 291.61 × 128.40
  4. Step 4: Simplify right side
    211.29x = 37,442.72
  5. Step 5: Solve for x
    x = 37,442.72/211.29
  6. Step 6: Final answer
    x = 177.21

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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.