Finding the Fourth Proportional to 21,111.72, 31,667.34 and 8,638.44

Step by Step Solution

1. Step 1: Write the proportion equation
   21,111.72 : 31,667.34 = 8,638.44 : x
2. Step 2: Convert to fraction form
   21,111.72/31,667.34 = 8,638.44/x
3. Step 3: Cross multiply
   21,111.72x = 31,667.34 × 8,638.44
4. Step 4: Simplify right side
   21,111.72x = 273,556,416.55
5. Step 5: Solve for x
   x = 273,556,416.55/21,111.72
6. Step 6: Final answer
   x = 12,957.56