Finding the Fourth Proportional to 21,431.76, 32,108.72 and 20,965.20

Step by Step Solution

1. Step 1: Write the proportion equation
   21,431.76 : 32,108.72 = 20,965.20 : x
2. Step 2: Convert to fraction form
   21,431.76/32,108.72 = 20,965.20/x
3. Step 3: Cross multiply
   21,431.76x = 32,108.72 × 20,965.20
4. Step 4: Simplify right side
   21,431.76x = 673,165,736.54
5. Step 5: Solve for x
   x = 673,165,736.54/21,431.76
6. Step 6: Final answer
   x = 31,409.73