Finding the Fourth Proportional to 12,890, 17,796.78 and 9,900.50

Step by Step Solution

1. Step 1: Write the proportion equation
   12,890 : 17,796.78 = 9,900.50 : x
2. Step 2: Convert to fraction form
   12,890/17,796.78 = 9,900.50/x
3. Step 3: Cross multiply
   12,890x = 17,796.78 × 9,900.50
4. Step 4: Simplify right side
   12,890x = 176,197,020.39
5. Step 5: Solve for x
   x = 176,197,020.39/12,890
6. Step 6: Final answer
   x = 13,669.28