Finding the Fourth Proportional to 105.69, 158.54 and 91.21

Step by Step Solution

1. Step 1: Write the proportion equation
   105.69 : 158.54 = 91.21 : x
2. Step 2: Convert to fraction form
   105.69/158.54 = 91.21/x
3. Step 3: Cross multiply
   105.69x = 158.54 × 91.21
4. Step 4: Simplify right side
   105.69x = 14,460.43
5. Step 5: Solve for x
   x = 14,460.43/105.69
6. Step 6: Final answer
   x = 136.82