Finding the Fourth Proportional to 105.72, 158.58 and 78.15

Step by Step Solution

1. Step 1: Write the proportion equation
   105.72 : 158.58 = 78.15 : x
2. Step 2: Convert to fraction form
   105.72/158.58 = 78.15/x
3. Step 3: Cross multiply
   105.72x = 158.58 × 78.15
4. Step 4: Simplify right side
   105.72x = 12,393.03
5. Step 5: Solve for x
   x = 12,393.03/105.72
6. Step 6: Final answer
   x = 117.23