Finding the Fourth Proportional to 21,010.46, 31,515.71 and 12,139.29

Step by Step Solution

1. Step 1: Write the proportion equation
   21,010.46 : 31,515.71 = 12,139.29 : x
2. Step 2: Convert to fraction form
   21,010.46/31,515.71 = 12,139.29/x
3. Step 3: Cross multiply
   21,010.46x = 31,515.71 × 12,139.29
4. Step 4: Simplify right side
   21,010.46x = 382,578,282.55
5. Step 5: Solve for x
   x = 382,578,282.55/21,010.46
6. Step 6: Final answer
   x = 18,208.95