Finding the Fourth Proportional to 86.13, 128.52 and 83.43

Step by Step Solution

1. Step 1: Write the proportion equation
   86.13 : 128.52 = 83.43 : x
2. Step 2: Convert to fraction form
   86.13/128.52 = 83.43/x
3. Step 3: Cross multiply
   86.13x = 128.52 × 83.43
4. Step 4: Simplify right side
   86.13x = 10,722.42
5. Step 5: Solve for x
   x = 10,722.42/86.13
6. Step 6: Final answer
   x = 124.49