Finding the Fourth Proportional to 139.55, 209.32 and 78.73

Step by Step Solution

1. Step 1: Write the proportion equation
   139.55 : 209.32 = 78.73 : x
2. Step 2: Convert to fraction form
   139.55/209.32 = 78.73/x
3. Step 3: Cross multiply
   139.55x = 209.32 × 78.73
4. Step 4: Simplify right side
   139.55x = 16,479.04
5. Step 5: Solve for x
   x = 16,479.04/139.55
6. Step 6: Final answer
   x = 118.09