Finding the Fourth Proportional to 85.53, 128.15 and 42.19

Step by Step Solution

1. Step 1: Write the proportion equation
   85.53 : 128.15 = 42.19 : x
2. Step 2: Convert to fraction form
   85.53/128.15 = 42.19/x
3. Step 3: Cross multiply
   85.53x = 128.15 × 42.19
4. Step 4: Simplify right side
   85.53x = 5,406.65
5. Step 5: Solve for x
   x = 5,406.65/85.53
6. Step 6: Final answer
   x = 63.21