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Finding the Fourth Proportional to 211.28, 316.95 and 81.30

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Solution

The fourth proportional to 211.28, 316.95 and 81.30 is: 121.97

Step by Step Solution

  1. Step 1: Write the proportion equation
    211.28 : 316.95 = 81.30 : x
  2. Step 2: Convert to fraction form
    211.28/316.95 = 81.30/x
  3. Step 3: Cross multiply
    211.28x = 316.95 × 81.30
  4. Step 4: Simplify right side
    211.28x = 25,768.92
  5. Step 5: Solve for x
    x = 25,768.92/211.28
  6. Step 6: Final answer
    x = 121.97

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.