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Finding the Fourth Proportional to 1,369.38, 1,889.90 and 780

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Solution

The fourth proportional to 1,369.38, 1,889.90 and 780 is: 1,076.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,369.38 : 1,889.90 = 780 : x
  2. Step 2: Convert to fraction form
    1,369.38/1,889.90 = 780/x
  3. Step 3: Cross multiply
    1,369.38x = 1,889.90 × 780
  4. Step 4: Simplify right side
    1,369.38x = 1,474,122
  5. Step 5: Solve for x
    x = 1,474,122/1,369.38
  6. Step 6: Final answer
    x = 1,076.49

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.