Finding the Fourth Proportional to 21,019.79, 31,513.88 and 9,920.15

Step by Step Solution

1. Step 1: Write the proportion equation
   21,019.79 : 31,513.88 = 9,920.15 : x
2. Step 2: Convert to fraction form
   21,019.79/31,513.88 = 9,920.15/x
3. Step 3: Cross multiply
   21,019.79x = 31,513.88 × 9,920.15
4. Step 4: Simplify right side
   21,019.79x = 312,622,520.27
5. Step 5: Solve for x
   x = 312,622,520.27/21,019.79
6. Step 6: Final answer
   x = 14,872.77