Finding the Fourth Proportional to 139.32, 209.06 and 90.56

Step by Step Solution

1. Step 1: Write the proportion equation
   139.32 : 209.06 = 90.56 : x
2. Step 2: Convert to fraction form
   139.32/209.06 = 90.56/x
3. Step 3: Cross multiply
   139.32x = 209.06 × 90.56
4. Step 4: Simplify right side
   139.32x = 18,932.88
5. Step 5: Solve for x
   x = 18,932.88/139.32
6. Step 6: Final answer
   x = 135.89