Finding the Fourth Proportional to 139.49, 192.63 and 89.78

Step by Step Solution

1. Step 1: Write the proportion equation
   139.49 : 192.63 = 89.78 : x
2. Step 2: Convert to fraction form
   139.49/192.63 = 89.78/x
3. Step 3: Cross multiply
   139.49x = 192.63 × 89.78
4. Step 4: Simplify right side
   139.49x = 17,295.02
5. Step 5: Solve for x
   x = 17,295.02/139.49
6. Step 6: Final answer
   x = 123.99