Finding the Fourth Proportional to 89.89, 134.55 and 86.72

Step by Step Solution

1. Step 1: Write the proportion equation
   89.89 : 134.55 = 86.72 : x
2. Step 2: Convert to fraction form
   89.89/134.55 = 86.72/x
3. Step 3: Cross multiply
   89.89x = 134.55 × 86.72
4. Step 4: Simplify right side
   89.89x = 11,668.18
5. Step 5: Solve for x
   x = 11,668.18/89.89
6. Step 6: Final answer
   x = 129.81