Finding the Fourth Proportional to 21,142.60, 31,721.25 and 13,236.05

Step by Step Solution

1. Step 1: Write the proportion equation
   21,142.60 : 31,721.25 = 13,236.05 : x
2. Step 2: Convert to fraction form
   21,142.60/31,721.25 = 13,236.05/x
3. Step 3: Cross multiply
   21,142.60x = 31,721.25 × 13,236.05
4. Step 4: Simplify right side
   21,142.60x = 419,864,051.06
5. Step 5: Solve for x
   x = 419,864,051.06/21,142.60
6. Step 6: Final answer
   x = 19,858.68