Finding the Fourth Proportional to 105.91, 158.86 and 90.72

Step by Step Solution

1. Step 1: Write the proportion equation
   105.91 : 158.86 = 90.72 : x
2. Step 2: Convert to fraction form
   105.91/158.86 = 90.72/x
3. Step 3: Cross multiply
   105.91x = 158.86 × 90.72
4. Step 4: Simplify right side
   105.91x = 14,411.89
5. Step 5: Solve for x
   x = 14,411.89/105.91
6. Step 6: Final answer
   x = 136.08