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Finding the Fourth Proportional to 211.78, 317.61 and 81.80

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Solution

The fourth proportional to 211.78, 317.61 and 81.80 is: 122.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    211.78 : 317.61 = 81.80 : x
  2. Step 2: Convert to fraction form
    211.78/317.61 = 81.80/x
  3. Step 3: Cross multiply
    211.78x = 317.61 × 81.80
  4. Step 4: Simplify right side
    211.78x = 25,980.50
  5. Step 5: Solve for x
    x = 25,980.50/211.78
  6. Step 6: Final answer
    x = 122.68

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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.