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Finding the Fourth Proportional to 1,247.28, 1,721.20 and 687.72

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Solution

The fourth proportional to 1,247.28, 1,721.20 and 687.72 is: 949.03

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,247.28 : 1,721.20 = 687.72 : x
  2. Step 2: Convert to fraction form
    1,247.28/1,721.20 = 687.72/x
  3. Step 3: Cross multiply
    1,247.28x = 1,721.20 × 687.72
  4. Step 4: Simplify right side
    1,247.28x = 1,183,703.66
  5. Step 5: Solve for x
    x = 1,183,703.66/1,247.28
  6. Step 6: Final answer
    x = 949.03

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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.