Finding the Third Proportional to 138,688 and 209,256

Step by Step Solution

1. Step 1: Write the proportion equation
   138,688 : 209,256 = 209,256 : x
2. Step 2: Convert to fraction form
   138,688/209,256 = 209,256/x
3. Step 3: Cross multiply
   138,688x = 209,256 × 209,256
4. Step 4: Simplify right side
   138,688x = 43,788,073,536
5. Step 5: Solve for x
   x = 43,788,073,536/138,688
6. Step 6: Final answer
   x = 315,730.80