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Finding the Fourth Proportional to 211.05, 291.30 and 128.21

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Solution

The fourth proportional to 211.05, 291.30 and 128.21 is: 176.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    211.05 : 291.30 = 128.21 : x
  2. Step 2: Convert to fraction form
    211.05/291.30 = 128.21/x
  3. Step 3: Cross multiply
    211.05x = 291.30 × 128.21
  4. Step 4: Simplify right side
    211.05x = 37,346.12
  5. Step 5: Solve for x
    x = 37,346.12/211.05
  6. Step 6: Final answer
    x = 176.95

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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.