Finding the Fourth Proportional to 105.42, 158.31 and 87.42

Step by Step Solution

1. Step 1: Write the proportion equation
   105.42 : 158.31 = 87.42 : x
2. Step 2: Convert to fraction form
   105.42/158.31 = 87.42/x
3. Step 3: Cross multiply
   105.42x = 158.31 × 87.42
4. Step 4: Simplify right side
   105.42x = 13,839.46
5. Step 5: Solve for x
   x = 13,839.46/105.42
6. Step 6: Final answer
   x = 131.28