Finding the Fourth Proportional to 20,801.60, 31,141.20 and 12,986.72

Step by Step Solution

1. Step 1: Write the proportion equation
   20,801.60 : 31,141.20 = 12,986.72 : x
2. Step 2: Convert to fraction form
   20,801.60/31,141.20 = 12,986.72/x
3. Step 3: Cross multiply
   20,801.60x = 31,141.20 × 12,986.72
4. Step 4: Simplify right side
   20,801.60x = 404,422,044.86
5. Step 5: Solve for x
   x = 404,422,044.86/20,801.60
6. Step 6: Final answer
   x = 19,441.87