Finding the Fourth Proportional to 89.38, 133.89 and 86.05

Step by Step Solution

1. Step 1: Write the proportion equation
   89.38 : 133.89 = 86.05 : x
2. Step 2: Convert to fraction form
   89.38/133.89 = 86.05/x
3. Step 3: Cross multiply
   89.38x = 133.89 × 86.05
4. Step 4: Simplify right side
   89.38x = 11,521.23
5. Step 5: Solve for x
   x = 11,521.23/89.38
6. Step 6: Final answer
   x = 128.90