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Finding the Fourth Proportional to 1,390.51, 1,918.87 and 769.51

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Solution

The fourth proportional to 1,390.51, 1,918.87 and 769.51 is: 1,061.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,390.51 : 1,918.87 = 769.51 : x
  2. Step 2: Convert to fraction form
    1,390.51/1,918.87 = 769.51/x
  3. Step 3: Cross multiply
    1,390.51x = 1,918.87 × 769.51
  4. Step 4: Simplify right side
    1,390.51x = 1,476,589.65
  5. Step 5: Solve for x
    x = 1,476,589.65/1,390.51
  6. Step 6: Final answer
    x = 1,061.91

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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.