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Finding the Fourth Proportional to 1,247.31, 1,721.25 and 687.78

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Solution

The fourth proportional to 1,247.31, 1,721.25 and 687.78 is: 949.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,247.31 : 1,721.25 = 687.78 : x
  2. Step 2: Convert to fraction form
    1,247.31/1,721.25 = 687.78/x
  3. Step 3: Cross multiply
    1,247.31x = 1,721.25 × 687.78
  4. Step 4: Simplify right side
    1,247.31x = 1,183,841.33
  5. Step 5: Solve for x
    x = 1,183,841.33/1,247.31
  6. Step 6: Final answer
    x = 949.12

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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.