Finding the Third Proportional to 11,515.50 and 21,120.75

Step by Step Solution

1. Step 1: Write the proportion equation
   11,515.50 : 21,120.75 = 21,120.75 : x
2. Step 2: Convert to fraction form
   11,515.50/21,120.75 = 21,120.75/x
3. Step 3: Cross multiply
   11,515.50x = 21,120.75 × 21,120.75
4. Step 4: Simplify right side
   11,515.50x = 446,086,080.56
5. Step 5: Solve for x
   x = 446,086,080.56/11,515.50
6. Step 6: Final answer
   x = 38,737.88