Finding the Fourth Proportional to 139.72, 209.38 and 105.39

Step by Step Solution

1. Step 1: Write the proportion equation
   139.72 : 209.38 = 105.39 : x
2. Step 2: Convert to fraction form
   139.72/209.38 = 105.39/x
3. Step 3: Cross multiply
   139.72x = 209.38 × 105.39
4. Step 4: Simplify right side
   139.72x = 22,066.56
5. Step 5: Solve for x
   x = 22,066.56/139.72
6. Step 6: Final answer
   x = 157.93