Finding the Fourth Proportional to 85.69, 128.55 and 40.10

Step by Step Solution

1. Step 1: Write the proportion equation
   85.69 : 128.55 = 40.10 : x
2. Step 2: Convert to fraction form
   85.69/128.55 = 40.10/x
3. Step 3: Cross multiply
   85.69x = 128.55 × 40.10
4. Step 4: Simplify right side
   85.69x = 5,154.36
5. Step 5: Solve for x
   x = 5,154.36/85.69
6. Step 6: Final answer
   x = 60.15