Finding the Fourth Proportional to 105.42, 157.83 and 81.42

Step by Step Solution

1. Step 1: Write the proportion equation
   105.42 : 157.83 = 81.42 : x
2. Step 2: Convert to fraction form
   105.42/157.83 = 81.42/x
3. Step 3: Cross multiply
   105.42x = 157.83 × 81.42
4. Step 4: Simplify right side
   105.42x = 12,850.52
5. Step 5: Solve for x
   x = 12,850.52/105.42
6. Step 6: Final answer
   x = 121.90