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Finding the Fourth Proportional to 211.56, 291.90 and 128.70

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Solution

The fourth proportional to 211.56, 291.90 and 128.70 is: 177.57

Step by Step Solution

  1. Step 1: Write the proportion equation
    211.56 : 291.90 = 128.70 : x
  2. Step 2: Convert to fraction form
    211.56/291.90 = 128.70/x
  3. Step 3: Cross multiply
    211.56x = 291.90 × 128.70
  4. Step 4: Simplify right side
    211.56x = 37,567.53
  5. Step 5: Solve for x
    x = 37,567.53/211.56
  6. Step 6: Final answer
    x = 177.57

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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.