Finding the Fourth Proportional to 139.79, 192.90 and 90.69

Step by Step Solution

1. Step 1: Write the proportion equation
   139.79 : 192.90 = 90.69 : x
2. Step 2: Convert to fraction form
   139.79/192.90 = 90.69/x
3. Step 3: Cross multiply
   139.79x = 192.90 × 90.69
4. Step 4: Simplify right side
   139.79x = 17,494.10
5. Step 5: Solve for x
   x = 17,494.10/139.79
6. Step 6: Final answer
   x = 125.15