Finding the Fourth Proportional to 85.51, 128.27 and 42.18

Step by Step Solution

1. Step 1: Write the proportion equation
   85.51 : 128.27 = 42.18 : x
2. Step 2: Convert to fraction form
   85.51/128.27 = 42.18/x
3. Step 3: Cross multiply
   85.51x = 128.27 × 42.18
4. Step 4: Simplify right side
   85.51x = 5,410.43
5. Step 5: Solve for x
   x = 5,410.43/85.51
6. Step 6: Final answer
   x = 63.27