Finding the Fourth Proportional to 86.07, 128.38 and 83.50

Step by Step Solution

1. Step 1: Write the proportion equation
   86.07 : 128.38 = 83.50 : x
2. Step 2: Convert to fraction form
   86.07/128.38 = 83.50/x
3. Step 3: Cross multiply
   86.07x = 128.38 × 83.50
4. Step 4: Simplify right side
   86.07x = 10,719.31
5. Step 5: Solve for x
   x = 10,719.31/86.07
6. Step 6: Final answer
   x = 124.54