Finding the Fourth Proportional to 139.56, 209.10 and 111

Step by Step Solution

1. Step 1: Write the proportion equation
   139.56 : 209.10 = 111 : x
2. Step 2: Convert to fraction form
   139.56/209.10 = 111/x
3. Step 3: Cross multiply
   139.56x = 209.10 × 111
4. Step 4: Simplify right side
   139.56x = 23,210.10
5. Step 5: Solve for x
   x = 23,210.10/139.56
6. Step 6: Final answer
   x = 166.31