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Finding the Fourth Proportional to 490.78, 678 and 386.56

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Solution

The fourth proportional to 490.78, 678 and 386.56 is: 534.02

Step by Step Solution

  1. Step 1: Write the proportion equation
    490.78 : 678 = 386.56 : x
  2. Step 2: Convert to fraction form
    490.78/678 = 386.56/x
  3. Step 3: Cross multiply
    490.78x = 678 × 386.56
  4. Step 4: Simplify right side
    490.78x = 262,087.68
  5. Step 5: Solve for x
    x = 262,087.68/490.78
  6. Step 6: Final answer
    x = 534.02

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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.