Finding the Third Proportional to 139.78 and 240.89

Step by Step Solution

1. Step 1: Write the proportion equation
   139.78 : 240.89 = 240.89 : x
2. Step 2: Convert to fraction form
   139.78/240.89 = 240.89/x
3. Step 3: Cross multiply
   139.78x = 240.89 × 240.89
4. Step 4: Simplify right side
   139.78x = 58,028.29
5. Step 5: Solve for x
   x = 58,028.29/139.78
6. Step 6: Final answer
   x = 415.14