Finding the Third Proportional to 86.69 and 128.22

Step by Step Solution

1. Step 1: Write the proportion equation
   86.69 : 128.22 = 128.22 : x
2. Step 2: Convert to fraction form
   86.69/128.22 = 128.22/x
3. Step 3: Cross multiply
   86.69x = 128.22 × 128.22
4. Step 4: Simplify right side
   86.69x = 16,440.05
5. Step 5: Solve for x
   x = 16,440.05/86.69
6. Step 6: Final answer
   x = 189.65