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Finding the Fourth Proportional to 1,278.42, 1,913.85 and 789.90

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Solution

The fourth proportional to 1,278.42, 1,913.85 and 789.90 is: 1,182.51

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,278.42 : 1,913.85 = 789.90 : x
  2. Step 2: Convert to fraction form
    1,278.42/1,913.85 = 789.90/x
  3. Step 3: Cross multiply
    1,278.42x = 1,913.85 × 789.90
  4. Step 4: Simplify right side
    1,278.42x = 1,511,750.12
  5. Step 5: Solve for x
    x = 1,511,750.12/1,278.42
  6. Step 6: Final answer
    x = 1,182.51

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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.