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Finding the Fourth Proportional to 1,389.20, 1,917 and 865.13

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Solution

The fourth proportional to 1,389.20, 1,917 and 865.13 is: 1,193.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,389.20 : 1,917 = 865.13 : x
  2. Step 2: Convert to fraction form
    1,389.20/1,917 = 865.13/x
  3. Step 3: Cross multiply
    1,389.20x = 1,917 × 865.13
  4. Step 4: Simplify right side
    1,389.20x = 1,658,444.63
  5. Step 5: Solve for x
    x = 1,658,444.63/1,389.20
  6. Step 6: Final answer
    x = 1,193.82

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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.