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Finding the Fourth Proportional to 211.30, 316.92 and 81.28

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Solution

The fourth proportional to 211.30, 316.92 and 81.28 is: 121.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    211.30 : 316.92 = 81.28 : x
  2. Step 2: Convert to fraction form
    211.30/316.92 = 81.28/x
  3. Step 3: Cross multiply
    211.30x = 316.92 × 81.28
  4. Step 4: Simplify right side
    211.30x = 25,759.26
  5. Step 5: Solve for x
    x = 25,759.26/211.30
  6. Step 6: Final answer
    x = 121.91

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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.