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Finding the Fourth Proportional to 2,139.90, 3,209.86 and 679.20

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Solution

The fourth proportional to 2,139.90, 3,209.86 and 679.20 is: 1,018.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    2,139.90 : 3,209.86 = 679.20 : x
  2. Step 2: Convert to fraction form
    2,139.90/3,209.86 = 679.20/x
  3. Step 3: Cross multiply
    2,139.90x = 3,209.86 × 679.20
  4. Step 4: Simplify right side
    2,139.90x = 2,180,136.91
  5. Step 5: Solve for x
    x = 2,180,136.91/2,139.90
  6. Step 6: Final answer
    x = 1,018.80

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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.