Finding the Fourth Proportional to 90.81, 136.17 and 72.72

Step by Step Solution

1. Step 1: Write the proportion equation
   90.81 : 136.17 = 72.72 : x
2. Step 2: Convert to fraction form
   90.81/136.17 = 72.72/x
3. Step 3: Cross multiply
   90.81x = 136.17 × 72.72
4. Step 4: Simplify right side
   90.81x = 9,902.28
5. Step 5: Solve for x
   x = 9,902.28/90.81
6. Step 6: Final answer
   x = 109.04