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Finding the Fourth Proportional to 857.80, 1,286.55 and 309.90

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Solution

The fourth proportional to 857.80, 1,286.55 and 309.90 is: 464.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    857.80 : 1,286.55 = 309.90 : x
  2. Step 2: Convert to fraction form
    857.80/1,286.55 = 309.90/x
  3. Step 3: Cross multiply
    857.80x = 1,286.55 × 309.90
  4. Step 4: Simplify right side
    857.80x = 398,701.85
  5. Step 5: Solve for x
    x = 398,701.85/857.80
  6. Step 6: Final answer
    x = 464.80

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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.