Finding the Fourth Proportional to 122.43, 168.91 and 78.15

Step by Step Solution

1. Step 1: Write the proportion equation
   122.43 : 168.91 = 78.15 : x
2. Step 2: Convert to fraction form
   122.43/168.91 = 78.15/x
3. Step 3: Cross multiply
   122.43x = 168.91 × 78.15
4. Step 4: Simplify right side
   122.43x = 13,200.32
5. Step 5: Solve for x
   x = 13,200.32/122.43
6. Step 6: Final answer
   x = 107.82