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Finding the Fourth Proportional to 939.70, 1,409.93 and 391.78

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Solution

The fourth proportional to 939.70, 1,409.93 and 391.78 is: 587.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    939.70 : 1,409.93 = 391.78 : x
  2. Step 2: Convert to fraction form
    939.70/1,409.93 = 391.78/x
  3. Step 3: Cross multiply
    939.70x = 1,409.93 × 391.78
  4. Step 4: Simplify right side
    939.70x = 552,382.38
  5. Step 5: Solve for x
    x = 552,382.38/939.70
  6. Step 6: Final answer
    x = 587.83

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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.