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Finding the Fourth Proportional to 679.92, 1,020.06 and 390.72

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Solution

The fourth proportional to 679.92, 1,020.06 and 390.72 is: 586.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    679.92 : 1,020.06 = 390.72 : x
  2. Step 2: Convert to fraction form
    679.92/1,020.06 = 390.72/x
  3. Step 3: Cross multiply
    679.92x = 1,020.06 × 390.72
  4. Step 4: Simplify right side
    679.92x = 398,557.84
  5. Step 5: Solve for x
    x = 398,557.84/679.92
  6. Step 6: Final answer
    x = 586.18

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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.