Finding the Fourth Proportional to 139.89, 193.17 and 90.81

Step by Step Solution

1. Step 1: Write the proportion equation
   139.89 : 193.17 = 90.81 : x
2. Step 2: Convert to fraction form
   139.89/193.17 = 90.81/x
3. Step 3: Cross multiply
   139.89x = 193.17 × 90.81
4. Step 4: Simplify right side
   139.89x = 17,541.77
5. Step 5: Solve for x
   x = 17,541.77/139.89
6. Step 6: Final answer
   x = 125.40