Finding the Fourth Proportional to 105.45, 158.37 and 78.31

Step by Step Solution

1. Step 1: Write the proportion equation
   105.45 : 158.37 = 78.31 : x
2. Step 2: Convert to fraction form
   105.45/158.37 = 78.31/x
3. Step 3: Cross multiply
   105.45x = 158.37 × 78.31
4. Step 4: Simplify right side
   105.45x = 12,401.95
5. Step 5: Solve for x
   x = 12,401.95/105.45
6. Step 6: Final answer
   x = 117.61