Finding the Fourth Proportional to 85.71, 128.61 and 40.05

Step by Step Solution

1. Step 1: Write the proportion equation
   85.71 : 128.61 = 40.05 : x
2. Step 2: Convert to fraction form
   85.71/128.61 = 40.05/x
3. Step 3: Cross multiply
   85.71x = 128.61 × 40.05
4. Step 4: Simplify right side
   85.71x = 5,150.73
5. Step 5: Solve for x
   x = 5,150.73/85.71
6. Step 6: Final answer
   x = 60.09