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Finding the Fourth Proportional to 839.30, 1,257.75 and 428.72

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Solution

The fourth proportional to 839.30, 1,257.75 and 428.72 is: 642.46

Step by Step Solution

  1. Step 1: Write the proportion equation
    839.30 : 1,257.75 = 428.72 : x
  2. Step 2: Convert to fraction form
    839.30/1,257.75 = 428.72/x
  3. Step 3: Cross multiply
    839.30x = 1,257.75 × 428.72
  4. Step 4: Simplify right side
    839.30x = 539,216.29
  5. Step 5: Solve for x
    x = 539,216.29/839.30
  6. Step 6: Final answer
    x = 642.46

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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.