Finding the Fourth Proportional to 139.56, 209.50 and 78.82

Step by Step Solution

1. Step 1: Write the proportion equation
   139.56 : 209.50 = 78.82 : x
2. Step 2: Convert to fraction form
   139.56/209.50 = 78.82/x
3. Step 3: Cross multiply
   139.56x = 209.50 × 78.82
4. Step 4: Simplify right side
   139.56x = 16,512.79
5. Step 5: Solve for x
   x = 16,512.79/139.56
6. Step 6: Final answer
   x = 118.32