Finding the Fourth Proportional to 21,685.20, 29,926.72 and 13,185.91

Step by Step Solution

1. Step 1: Write the proportion equation
   21,685.20 : 29,926.72 = 13,185.91 : x
2. Step 2: Convert to fraction form
   21,685.20/29,926.72 = 13,185.91/x
3. Step 3: Cross multiply
   21,685.20x = 29,926.72 × 13,185.91
4. Step 4: Simplify right side
   21,685.20x = 394,610,970.59
5. Step 5: Solve for x
   x = 394,610,970.59/21,685.20
6. Step 6: Final answer
   x = 18,197.25