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Finding the Fourth Proportional to 391.90, 540.80 and 217.21

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Solution

The fourth proportional to 391.90, 540.80 and 217.21 is: 299.74

Step by Step Solution

  1. Step 1: Write the proportion equation
    391.90 : 540.80 = 217.21 : x
  2. Step 2: Convert to fraction form
    391.90/540.80 = 217.21/x
  3. Step 3: Cross multiply
    391.90x = 540.80 × 217.21
  4. Step 4: Simplify right side
    391.90x = 117,467.17
  5. Step 5: Solve for x
    x = 117,467.17/391.90
  6. Step 6: Final answer
    x = 299.74

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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.