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Finding the Fourth Proportional to 856.90, 1,285.31 and 279.78

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Solution

The fourth proportional to 856.90, 1,285.31 and 279.78 is: 419.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    856.90 : 1,285.31 = 279.78 : x
  2. Step 2: Convert to fraction form
    856.90/1,285.31 = 279.78/x
  3. Step 3: Cross multiply
    856.90x = 1,285.31 × 279.78
  4. Step 4: Simplify right side
    856.90x = 359,604.03
  5. Step 5: Solve for x
    x = 359,604.03/856.90
  6. Step 6: Final answer
    x = 419.66

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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.