Finding the Third Proportional to 138,709 and 209,521.50

Step by Step Solution

1. Step 1: Write the proportion equation
   138,709 : 209,521.50 = 209,521.50 : x
2. Step 2: Convert to fraction form
   138,709/209,521.50 = 209,521.50/x
3. Step 3: Cross multiply
   138,709x = 209,521.50 × 209,521.50
4. Step 4: Simplify right side
   138,709x = 43,899,258,962.25
5. Step 5: Solve for x
   x = 43,899,258,962.25/138,709
6. Step 6: Final answer
   x = 316,484.58