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Finding the Fourth Proportional to 678.90, 936.78 and 399.18

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Solution

The fourth proportional to 678.90, 936.78 and 399.18 is: 550.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    678.90 : 936.78 = 399.18 : x
  2. Step 2: Convert to fraction form
    678.90/936.78 = 399.18/x
  3. Step 3: Cross multiply
    678.90x = 936.78 × 399.18
  4. Step 4: Simplify right side
    678.90x = 373,943.84
  5. Step 5: Solve for x
    x = 373,943.84/678.90
  6. Step 6: Final answer
    x = 550.81

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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.