Finding the Fourth Proportional to 85.60, 128.31 and 42.24

Step by Step Solution

1. Step 1: Write the proportion equation
   85.60 : 128.31 = 42.24 : x
2. Step 2: Convert to fraction form
   85.60/128.31 = 42.24/x
3. Step 3: Cross multiply
   85.60x = 128.31 × 42.24
4. Step 4: Simplify right side
   85.60x = 5,418.96
5. Step 5: Solve for x
   x = 5,418.96/85.60
6. Step 6: Final answer
   x = 63.31