Finding the Fourth Proportional to 86.24, 128.72 and 80.16

Step by Step Solution

1. Step 1: Write the proportion equation
   86.24 : 128.72 = 80.16 : x
2. Step 2: Convert to fraction form
   86.24/128.72 = 80.16/x
3. Step 3: Cross multiply
   86.24x = 128.72 × 80.16
4. Step 4: Simplify right side
   86.24x = 10,318.20
5. Step 5: Solve for x
   x = 10,318.20/86.24
6. Step 6: Final answer
   x = 119.65