Finding the Fourth Proportional to 139.76, 209.82 and 78.94

Step by Step Solution

1. Step 1: Write the proportion equation
   139.76 : 209.82 = 78.94 : x
2. Step 2: Convert to fraction form
   139.76/209.82 = 78.94/x
3. Step 3: Cross multiply
   139.76x = 209.82 × 78.94
4. Step 4: Simplify right side
   139.76x = 16,562.20
5. Step 5: Solve for x
   x = 16,562.20/139.76
6. Step 6: Final answer
   x = 118.50