Finding the Fourth Proportional to 13,776.72, 20,661.97 and 3,915.78

Step by Step Solution

1. Step 1: Write the proportion equation
   13,776.72 : 20,661.97 = 3,915.78 : x
2. Step 2: Convert to fraction form
   13,776.72/20,661.97 = 3,915.78/x
3. Step 3: Cross multiply
   13,776.72x = 20,661.97 × 3,915.78
4. Step 4: Simplify right side
   13,776.72x = 80,907,728.89
5. Step 5: Solve for x
   x = 80,907,728.89/13,776.72
6. Step 6: Final answer
   x = 5,872.79