Finding the Fourth Proportional to 21,499, 29,671.86 and 13,120.36

Step by Step Solution

1. Step 1: Write the proportion equation
   21,499 : 29,671.86 = 13,120.36 : x
2. Step 2: Convert to fraction form
   21,499/29,671.86 = 13,120.36/x
3. Step 3: Cross multiply
   21,499x = 29,671.86 × 13,120.36
4. Step 4: Simplify right side
   21,499x = 389,305,485.07
5. Step 5: Solve for x
   x = 389,305,485.07/21,499
6. Step 6: Final answer
   x = 18,108.07