Finding the Fourth Proportional to 1,311.31, 1,809.52 and 721.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,311.31 : 1,809.52 = 721.72 : x
2. Step 2: Convert to fraction form
   1,311.31/1,809.52 = 721.72/x
3. Step 3: Cross multiply
   1,311.31x = 1,809.52 × 721.72
4. Step 4: Simplify right side
   1,311.31x = 1,305,966.77
5. Step 5: Solve for x
   x = 1,305,966.77/1,311.31
6. Step 6: Final answer
   x = 995.93