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Finding the Fourth Proportional to 211.25, 316.90 and 81.22

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Solution

The fourth proportional to 211.25, 316.90 and 81.22 is: 121.84

Step by Step Solution

  1. Step 1: Write the proportion equation
    211.25 : 316.90 = 81.22 : x
  2. Step 2: Convert to fraction form
    211.25/316.90 = 81.22/x
  3. Step 3: Cross multiply
    211.25x = 316.90 × 81.22
  4. Step 4: Simplify right side
    211.25x = 25,738.92
  5. Step 5: Solve for x
    x = 25,738.92/211.25
  6. Step 6: Final answer
    x = 121.84

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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.