Finding the Fourth Proportional to 3,921.78, 5,411.71 and 2,153.35

Step by Step Solution

1. Step 1: Write the proportion equation
   3,921.78 : 5,411.71 = 2,153.35 : x
2. Step 2: Convert to fraction form
   3,921.78/5,411.71 = 2,153.35/x
3. Step 3: Cross multiply
   3,921.78x = 5,411.71 × 2,153.35
4. Step 4: Simplify right side
   3,921.78x = 11,653,300.35
5. Step 5: Solve for x
   x = 11,653,300.35/3,921.78
6. Step 6: Final answer
   x = 2,971.43