Finding the Third Proportional to 8,820 and 12,390

Step by Step Solution

1. Step 1: Write the proportion equation
   8,820 : 12,390 = 12,390 : x
2. Step 2: Convert to fraction form
   8,820/12,390 = 12,390/x
3. Step 3: Cross multiply
   8,820x = 12,390 × 12,390
4. Step 4: Simplify right side
   8,820x = 153,512,100
5. Step 5: Solve for x
   x = 153,512,100/8,820
6. Step 6: Final answer
   x = 17,405