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Finding the Fourth Proportional to 939.81, 1,409.28 and 391.66

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Solution

The fourth proportional to 939.81, 1,409.28 and 391.66 is: 587.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    939.81 : 1,409.28 = 391.66 : x
  2. Step 2: Convert to fraction form
    939.81/1,409.28 = 391.66/x
  3. Step 3: Cross multiply
    939.81x = 1,409.28 × 391.66
  4. Step 4: Simplify right side
    939.81x = 551,958.60
  5. Step 5: Solve for x
    x = 551,958.60/939.81
  6. Step 6: Final answer
    x = 587.31

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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.