Finding the Fourth Proportional to 85.81, 128.72 and 21.69

Step by Step Solution

1. Step 1: Write the proportion equation
   85.81 : 128.72 = 21.69 : x
2. Step 2: Convert to fraction form
   85.81/128.72 = 21.69/x
3. Step 3: Cross multiply
   85.81x = 128.72 × 21.69
4. Step 4: Simplify right side
   85.81x = 2,791.94
5. Step 5: Solve for x
   x = 2,791.94/85.81
6. Step 6: Final answer
   x = 32.54