Finding the Fourth Proportional to 2,085.76, 3,129.72 and 931.24

Step by Step Solution

1. Step 1: Write the proportion equation
   2,085.76 : 3,129.72 = 931.24 : x
2. Step 2: Convert to fraction form
   2,085.76/3,129.72 = 931.24/x
3. Step 3: Cross multiply
   2,085.76x = 3,129.72 × 931.24
4. Step 4: Simplify right side
   2,085.76x = 2,914,520.45
5. Step 5: Solve for x
   x = 2,914,520.45/2,085.76
6. Step 6: Final answer
   x = 1,397.34