Finding the Third Proportional to 11,128.50 and 21,690

Step by Step Solution

1. Step 1: Write the proportion equation
   11,128.50 : 21,690 = 21,690 : x
2. Step 2: Convert to fraction form
   11,128.50/21,690 = 21,690/x
3. Step 3: Cross multiply
   11,128.50x = 21,690 × 21,690
4. Step 4: Simplify right side
   11,128.50x = 470,456,100
5. Step 5: Solve for x
   x = 470,456,100/11,128.50
6. Step 6: Final answer
   x = 42,274.89