Finding the Fourth Proportional to 90.69, 136.17 and 80.43

Step by Step Solution

1. Step 1: Write the proportion equation
   90.69 : 136.17 = 80.43 : x
2. Step 2: Convert to fraction form
   90.69/136.17 = 80.43/x
3. Step 3: Cross multiply
   90.69x = 136.17 × 80.43
4. Step 4: Simplify right side
   90.69x = 10,952.15
5. Step 5: Solve for x
   x = 10,952.15/90.69
6. Step 6: Final answer
   x = 120.76