Finding the Third Proportional to 138,589 and 209,137.50

Step by Step Solution

1. Step 1: Write the proportion equation
   138,589 : 209,137.50 = 209,137.50 : x
2. Step 2: Convert to fraction form
   138,589/209,137.50 = 209,137.50/x
3. Step 3: Cross multiply
   138,589x = 209,137.50 × 209,137.50
4. Step 4: Simplify right side
   138,589x = 43,738,493,906.25
5. Step 5: Solve for x
   x = 43,738,493,906.25/138,589
6. Step 6: Final answer
   x = 315,598.60