Finding the Third Proportional to 3,990 and 8,411.25

Step by Step Solution

1. Step 1: Write the proportion equation
   3,990 : 8,411.25 = 8,411.25 : x
2. Step 2: Convert to fraction form
   3,990/8,411.25 = 8,411.25/x
3. Step 3: Cross multiply
   3,990x = 8,411.25 × 8,411.25
4. Step 4: Simplify right side
   3,990x = 70,749,126.56
5. Step 5: Solve for x
   x = 70,749,126.56/3,990
6. Step 6: Final answer
   x = 17,731.61