Finding the Fourth Proportional to 21,675.88, 29,915.89 and 12,728.28

Step by Step Solution

1. Step 1: Write the proportion equation
   21,675.88 : 29,915.89 = 12,728.28 : x
2. Step 2: Convert to fraction form
   21,675.88/29,915.89 = 12,728.28/x
3. Step 3: Cross multiply
   21,675.88x = 29,915.89 × 12,728.28
4. Step 4: Simplify right side
   21,675.88x = 380,777,792.55
5. Step 5: Solve for x
   x = 380,777,792.55/21,675.88
6. Step 6: Final answer
   x = 17,566.89