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Finding the Fourth Proportional to 391.89, 540.81 and 221.55

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Solution

The fourth proportional to 391.89, 540.81 and 221.55 is: 305.74

Step by Step Solution

  1. Step 1: Write the proportion equation
    391.89 : 540.81 = 221.55 : x
  2. Step 2: Convert to fraction form
    391.89/540.81 = 221.55/x
  3. Step 3: Cross multiply
    391.89x = 540.81 × 221.55
  4. Step 4: Simplify right side
    391.89x = 119,816.46
  5. Step 5: Solve for x
    x = 119,816.46/391.89
  6. Step 6: Final answer
    x = 305.74

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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.