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Finding the Fourth Proportional to 678.74, 936.55 and 399.21

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Solution

The fourth proportional to 678.74, 936.55 and 399.21 is: 550.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    678.74 : 936.55 = 399.21 : x
  2. Step 2: Convert to fraction form
    678.74/936.55 = 399.21/x
  3. Step 3: Cross multiply
    678.74x = 936.55 × 399.21
  4. Step 4: Simplify right side
    678.74x = 373,883.96
  5. Step 5: Solve for x
    x = 373,883.96/678.74
  6. Step 6: Final answer
    x = 550.85

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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.