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Finding the Fourth Proportional to 678.68, 1,018.20 and 418.88

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Solution

The fourth proportional to 678.68, 1,018.20 and 418.88 is: 628.43

Step by Step Solution

  1. Step 1: Write the proportion equation
    678.68 : 1,018.20 = 418.88 : x
  2. Step 2: Convert to fraction form
    678.68/1,018.20 = 418.88/x
  3. Step 3: Cross multiply
    678.68x = 1,018.20 × 418.88
  4. Step 4: Simplify right side
    678.68x = 426,503.62
  5. Step 5: Solve for x
    x = 426,503.62/678.68
  6. Step 6: Final answer
    x = 628.43

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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.