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Finding the Fourth Proportional to 1,247, 1,721.42 and 781.52

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Solution

The fourth proportional to 1,247, 1,721.42 and 781.52 is: 1,078.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,247 : 1,721.42 = 781.52 : x
  2. Step 2: Convert to fraction form
    1,247/1,721.42 = 781.52/x
  3. Step 3: Cross multiply
    1,247x = 1,721.42 × 781.52
  4. Step 4: Simplify right side
    1,247x = 1,345,324.16
  5. Step 5: Solve for x
    x = 1,345,324.16/1,247
  6. Step 6: Final answer
    x = 1,078.85

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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.