Finding the Fourth Proportional to 85.80, 128.72 and 28.01

Step by Step Solution

1. Step 1: Write the proportion equation
   85.80 : 128.72 = 28.01 : x
2. Step 2: Convert to fraction form
   85.80/128.72 = 28.01/x
3. Step 3: Cross multiply
   85.80x = 128.72 × 28.01
4. Step 4: Simplify right side
   85.80x = 3,605.45
5. Step 5: Solve for x
   x = 3,605.45/85.80
6. Step 6: Final answer
   x = 42.02