Finding the Third Proportional to 10,000 and 12,990

Step by Step Solution

1. Step 1: Write the proportion equation
   10,000 : 12,990 = 12,990 : x
2. Step 2: Convert to fraction form
   10,000/12,990 = 12,990/x
3. Step 3: Cross multiply
   10,000x = 12,990 × 12,990
4. Step 4: Simplify right side
   10,000x = 168,740,100
5. Step 5: Solve for x
   x = 168,740,100/10,000
6. Step 6: Final answer
   x = 16,874.01