Finding the Fourth Proportional to 139.82, 209.33 and 105.72

Step by Step Solution

1. Step 1: Write the proportion equation
   139.82 : 209.33 = 105.72 : x
2. Step 2: Convert to fraction form
   139.82/209.33 = 105.72/x
3. Step 3: Cross multiply
   139.82x = 209.33 × 105.72
4. Step 4: Simplify right side
   139.82x = 22,130.37
5. Step 5: Solve for x
   x = 22,130.37/139.82
6. Step 6: Final answer
   x = 158.28