Finding the Fourth Proportional to 85.68, 128.48 and 42.96

Step by Step Solution

1. Step 1: Write the proportion equation
   85.68 : 128.48 = 42.96 : x
2. Step 2: Convert to fraction form
   85.68/128.48 = 42.96/x
3. Step 3: Cross multiply
   85.68x = 128.48 × 42.96
4. Step 4: Simplify right side
   85.68x = 5,519.50
5. Step 5: Solve for x
   x = 5,519.50/85.68
6. Step 6: Final answer
   x = 64.42