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Finding the Fourth Proportional to 2,139.88, 3,209.82 and 840.64

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Solution

The fourth proportional to 2,139.88, 3,209.82 and 840.64 is: 1,260.96

Step by Step Solution

  1. Step 1: Write the proportion equation
    2,139.88 : 3,209.82 = 840.64 : x
  2. Step 2: Convert to fraction form
    2,139.88/3,209.82 = 840.64/x
  3. Step 3: Cross multiply
    2,139.88x = 3,209.82 × 840.64
  4. Step 4: Simplify right side
    2,139.88x = 2,698,303.08
  5. Step 5: Solve for x
    x = 2,698,303.08/2,139.88
  6. Step 6: Final answer
    x = 1,260.96

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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.