Finding the Fourth Proportional to 139.78, 192.68 and 90.55

Step by Step Solution

1. Step 1: Write the proportion equation
   139.78 : 192.68 = 90.55 : x
2. Step 2: Convert to fraction form
   139.78/192.68 = 90.55/x
3. Step 3: Cross multiply
   139.78x = 192.68 × 90.55
4. Step 4: Simplify right side
   139.78x = 17,446.72
5. Step 5: Solve for x
   x = 17,446.72/139.78
6. Step 6: Final answer
   x = 124.82