Finding the Fourth Proportional to 139.28, 191.99 and 90.05

Step by Step Solution

1. Step 1: Write the proportion equation
   139.28 : 191.99 = 90.05 : x
2. Step 2: Convert to fraction form
   139.28/191.99 = 90.05/x
3. Step 3: Cross multiply
   139.28x = 191.99 × 90.05
4. Step 4: Simplify right side
   139.28x = 17,288.25
5. Step 5: Solve for x
   x = 17,288.25/139.28
6. Step 6: Final answer
   x = 124.13