Finding the Fourth Proportional to 2,153.72, 3,230.90 and 921.12

Step by Step Solution

1. Step 1: Write the proportion equation
   2,153.72 : 3,230.90 = 921.12 : x
2. Step 2: Convert to fraction form
   2,153.72/3,230.90 = 921.12/x
3. Step 3: Cross multiply
   2,153.72x = 3,230.90 × 921.12
4. Step 4: Simplify right side
   2,153.72x = 2,976,046.61
5. Step 5: Solve for x
   x = 2,976,046.61/2,153.72
6. Step 6: Final answer
   x = 1,381.82