Finding the Fourth Proportional to 85.68, 128.58 and 42.38

Step by Step Solution

1. Step 1: Write the proportion equation
   85.68 : 128.58 = 42.38 : x
2. Step 2: Convert to fraction form
   85.68/128.58 = 42.38/x
3. Step 3: Cross multiply
   85.68x = 128.58 × 42.38
4. Step 4: Simplify right side
   85.68x = 5,449.22
5. Step 5: Solve for x
   x = 5,449.22/85.68
6. Step 6: Final answer
   x = 63.60