Finding the Fourth Proportional to 85.48, 128.18 and 42.13

Step by Step Solution

1. Step 1: Write the proportion equation
   85.48 : 128.18 = 42.13 : x
2. Step 2: Convert to fraction form
   85.48/128.18 = 42.13/x
3. Step 3: Cross multiply
   85.48x = 128.18 × 42.13
4. Step 4: Simplify right side
   85.48x = 5,399.69
5. Step 5: Solve for x
   x = 5,399.69/85.48
6. Step 6: Final answer
   x = 63.17