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Finding the Fourth Proportional to 868.12, 1,291 and 840.78

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Solution

The fourth proportional to 868.12, 1,291 and 840.78 is: 1,250.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    868.12 : 1,291 = 840.78 : x
  2. Step 2: Convert to fraction form
    868.12/1,291 = 840.78/x
  3. Step 3: Cross multiply
    868.12x = 1,291 × 840.78
  4. Step 4: Simplify right side
    868.12x = 1,085,446.98
  5. Step 5: Solve for x
    x = 1,085,446.98/868.12
  6. Step 6: Final answer
    x = 1,250.34

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.