Finding the Third Proportional to 10,689.75 and 21,379.50

Step by Step Solution

1. Step 1: Write the proportion equation
   10,689.75 : 21,379.50 = 21,379.50 : x
2. Step 2: Convert to fraction form
   10,689.75/21,379.50 = 21,379.50/x
3. Step 3: Cross multiply
   10,689.75x = 21,379.50 × 21,379.50
4. Step 4: Simplify right side
   10,689.75x = 457,083,020.25
5. Step 5: Solve for x
   x = 457,083,020.25/10,689.75
6. Step 6: Final answer
   x = 42,759