Finding the Fourth Proportional to 89.91, 134.32 and 86.88

Step by Step Solution

1. Step 1: Write the proportion equation
   89.91 : 134.32 = 86.88 : x
2. Step 2: Convert to fraction form
   89.91/134.32 = 86.88/x
3. Step 3: Cross multiply
   89.91x = 134.32 × 86.88
4. Step 4: Simplify right side
   89.91x = 11,669.72
5. Step 5: Solve for x
   x = 11,669.72/89.91
6. Step 6: Final answer
   x = 129.79