Finding the Fourth Proportional to 12,916.31, 17,821.22 and 7,880.20

Step by Step Solution

1. Step 1: Write the proportion equation
   12,916.31 : 17,821.22 = 7,880.20 : x
2. Step 2: Convert to fraction form
   12,916.31/17,821.22 = 7,880.20/x
3. Step 3: Cross multiply
   12,916.31x = 17,821.22 × 7,880.20
4. Step 4: Simplify right side
   12,916.31x = 140,434,693.89
5. Step 5: Solve for x
   x = 140,434,693.89/12,916.31
6. Step 6: Final answer
   x = 10,872.67