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Finding the Fourth Proportional to 939.58, 1,409.40 and 391.78

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Solution

The fourth proportional to 939.58, 1,409.40 and 391.78 is: 587.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    939.58 : 1,409.40 = 391.78 : x
  2. Step 2: Convert to fraction form
    939.58/1,409.40 = 391.78/x
  3. Step 3: Cross multiply
    939.58x = 1,409.40 × 391.78
  4. Step 4: Simplify right side
    939.58x = 552,174.73
  5. Step 5: Solve for x
    x = 552,174.73/939.58
  6. Step 6: Final answer
    x = 587.68

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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.