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Finding the Fourth Proportional to 2,651.78, 3,978.08 and 920

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Solution

The fourth proportional to 2,651.78, 3,978.08 and 920 is: 1,380.14

Step by Step Solution

  1. Step 1: Write the proportion equation
    2,651.78 : 3,978.08 = 920 : x
  2. Step 2: Convert to fraction form
    2,651.78/3,978.08 = 920/x
  3. Step 3: Cross multiply
    2,651.78x = 3,978.08 × 920
  4. Step 4: Simplify right side
    2,651.78x = 3,659,833.60
  5. Step 5: Solve for x
    x = 3,659,833.60/2,651.78
  6. Step 6: Final answer
    x = 1,380.14

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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.