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Finding the Fourth Proportional to 839.48, 1,258.20 and 428.90

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Solution

The fourth proportional to 839.48, 1,258.20 and 428.90 is: 642.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    839.48 : 1,258.20 = 428.90 : x
  2. Step 2: Convert to fraction form
    839.48/1,258.20 = 428.90/x
  3. Step 3: Cross multiply
    839.48x = 1,258.20 × 428.90
  4. Step 4: Simplify right side
    839.48x = 539,641.98
  5. Step 5: Solve for x
    x = 539,641.98/839.48
  6. Step 6: Final answer
    x = 642.83

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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.