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Finding the Fourth Proportional to 857.40, 1,285.78 and 418.40

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Solution

The fourth proportional to 857.40, 1,285.78 and 418.40 is: 627.44

Step by Step Solution

  1. Step 1: Write the proportion equation
    857.40 : 1,285.78 = 418.40 : x
  2. Step 2: Convert to fraction form
    857.40/1,285.78 = 418.40/x
  3. Step 3: Cross multiply
    857.40x = 1,285.78 × 418.40
  4. Step 4: Simplify right side
    857.40x = 537,970.35
  5. Step 5: Solve for x
    x = 537,970.35/857.40
  6. Step 6: Final answer
    x = 627.44

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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.