Finding the Fourth Proportional to 139.55, 209.16 and 105.20

Step by Step Solution

1. Step 1: Write the proportion equation
   139.55 : 209.16 = 105.20 : x
2. Step 2: Convert to fraction form
   139.55/209.16 = 105.20/x
3. Step 3: Cross multiply
   139.55x = 209.16 × 105.20
4. Step 4: Simplify right side
   139.55x = 22,003.83
5. Step 5: Solve for x
   x = 22,003.83/139.55
6. Step 6: Final answer
   x = 157.67