Finding the Fourth Proportional to 21,100.79, 31,653.35 and 7,964.21

Step by Step Solution

1. Step 1: Write the proportion equation
   21,100.79 : 31,653.35 = 7,964.21 : x
2. Step 2: Convert to fraction form
   21,100.79/31,653.35 = 7,964.21/x
3. Step 3: Cross multiply
   21,100.79x = 31,653.35 × 7,964.21
4. Step 4: Simplify right side
   21,100.79x = 252,093,728.52
5. Step 5: Solve for x
   x = 252,093,728.52/21,100.79
6. Step 6: Final answer
   x = 11,947.13