Finding the Fourth Proportional to 86.43, 128.79 and 83.67

Step by Step Solution

1. Step 1: Write the proportion equation
   86.43 : 128.79 = 83.67 : x
2. Step 2: Convert to fraction form
   86.43/128.79 = 83.67/x
3. Step 3: Cross multiply
   86.43x = 128.79 × 83.67
4. Step 4: Simplify right side
   86.43x = 10,775.86
5. Step 5: Solve for x
   x = 10,775.86/86.43
6. Step 6: Final answer
   x = 124.68