Finding the Third Proportional to 139.50 and 212.91

Step by Step Solution

1. Step 1: Write the proportion equation
   139.50 : 212.91 = 212.91 : x
2. Step 2: Convert to fraction form
   139.50/212.91 = 212.91/x
3. Step 3: Cross multiply
   139.50x = 212.91 × 212.91
4. Step 4: Simplify right side
   139.50x = 45,329.07
5. Step 5: Solve for x
   x = 45,329.07/139.50
6. Step 6: Final answer
   x = 324.94