Finding the Third Proportional to 12,642 and 19,990

Step by Step Solution

1. Step 1: Write the proportion equation
   12,642 : 19,990 = 19,990 : x
2. Step 2: Convert to fraction form
   12,642/19,990 = 19,990/x
3. Step 3: Cross multiply
   12,642x = 19,990 × 19,990
4. Step 4: Simplify right side
   12,642x = 399,600,100
5. Step 5: Solve for x
   x = 399,600,100/12,642
6. Step 6: Final answer
   x = 31,608.93