Finding the Fourth Proportional to 21,085.04, 31,638.60 and 13,687.76

Step by Step Solution

1. Step 1: Write the proportion equation
   21,085.04 : 31,638.60 = 13,687.76 : x
2. Step 2: Convert to fraction form
   21,085.04/31,638.60 = 13,687.76/x
3. Step 3: Cross multiply
   21,085.04x = 31,638.60 × 13,687.76
4. Step 4: Simplify right side
   21,085.04x = 433,061,563.54
5. Step 5: Solve for x
   x = 433,061,563.54/21,085.04
6. Step 6: Final answer
   x = 20,538.81