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Finding the Fourth Proportional to 939.78, 1,409.76 and 391.62

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Solution

The fourth proportional to 939.78, 1,409.76 and 391.62 is: 587.47

Step by Step Solution

  1. Step 1: Write the proportion equation
    939.78 : 1,409.76 = 391.62 : x
  2. Step 2: Convert to fraction form
    939.78/1,409.76 = 391.62/x
  3. Step 3: Cross multiply
    939.78x = 1,409.76 × 391.62
  4. Step 4: Simplify right side
    939.78x = 552,090.21
  5. Step 5: Solve for x
    x = 552,090.21/939.78
  6. Step 6: Final answer
    x = 587.47

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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.