Finding the Fourth Proportional to 12,990.35, 17,921.88 and 8,516.57

Step by Step Solution

1. Step 1: Write the proportion equation
   12,990.35 : 17,921.88 = 8,516.57 : x
2. Step 2: Convert to fraction form
   12,990.35/17,921.88 = 8,516.57/x
3. Step 3: Cross multiply
   12,990.35x = 17,921.88 × 8,516.57
4. Step 4: Simplify right side
   12,990.35x = 152,632,945.55
5. Step 5: Solve for x
   x = 152,632,945.55/12,990.35
6. Step 6: Final answer
   x = 11,749.72