Finding the Third Proportional to 139.78 and 216.28

Step by Step Solution

1. Step 1: Write the proportion equation
   139.78 : 216.28 = 216.28 : x
2. Step 2: Convert to fraction form
   139.78/216.28 = 216.28/x
3. Step 3: Cross multiply
   139.78x = 216.28 × 216.28
4. Step 4: Simplify right side
   139.78x = 46,777.58
5. Step 5: Solve for x
   x = 46,777.58/139.78
6. Step 6: Final answer
   x = 334.65