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Finding the Fourth Proportional to 840.78, 1,260.20 and 378.80

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Solution

The fourth proportional to 840.78, 1,260.20 and 378.80 is: 567.76

Step by Step Solution

  1. Step 1: Write the proportion equation
    840.78 : 1,260.20 = 378.80 : x
  2. Step 2: Convert to fraction form
    840.78/1,260.20 = 378.80/x
  3. Step 3: Cross multiply
    840.78x = 1,260.20 × 378.80
  4. Step 4: Simplify right side
    840.78x = 477,363.76
  5. Step 5: Solve for x
    x = 477,363.76/840.78
  6. Step 6: Final answer
    x = 567.76

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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.