Finding the Fourth Proportional to 85.99, 128.98 and 42.65

Step by Step Solution

1. Step 1: Write the proportion equation
   85.99 : 128.98 = 42.65 : x
2. Step 2: Convert to fraction form
   85.99/128.98 = 42.65/x
3. Step 3: Cross multiply
   85.99x = 128.98 × 42.65
4. Step 4: Simplify right side
   85.99x = 5,500.25
5. Step 5: Solve for x
   x = 5,500.25/85.99
6. Step 6: Final answer
   x = 63.96