Finding the Fourth Proportional to 90.50, 136.37 and 80.69

Step by Step Solution

1. Step 1: Write the proportion equation
   90.50 : 136.37 = 80.69 : x
2. Step 2: Convert to fraction form
   90.50/136.37 = 80.69/x
3. Step 3: Cross multiply
   90.50x = 136.37 × 80.69
4. Step 4: Simplify right side
   90.50x = 11,002.61
5. Step 5: Solve for x
   x = 11,002.61/90.50
6. Step 6: Final answer
   x = 121.58