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Finding the Fourth Proportional to 1,386.90, 1,913.96 and 789.49

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Solution

The fourth proportional to 1,386.90, 1,913.96 and 789.49 is: 1,089.52

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,386.90 : 1,913.96 = 789.49 : x
  2. Step 2: Convert to fraction form
    1,386.90/1,913.96 = 789.49/x
  3. Step 3: Cross multiply
    1,386.90x = 1,913.96 × 789.49
  4. Step 4: Simplify right side
    1,386.90x = 1,511,052.28
  5. Step 5: Solve for x
    x = 1,511,052.28/1,386.90
  6. Step 6: Final answer
    x = 1,089.52

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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.