Finding the Fourth Proportional to 123.12, 169.83 and 78.86

Step by Step Solution

1. Step 1: Write the proportion equation
   123.12 : 169.83 = 78.86 : x
2. Step 2: Convert to fraction form
   123.12/169.83 = 78.86/x
3. Step 3: Cross multiply
   123.12x = 169.83 × 78.86
4. Step 4: Simplify right side
   123.12x = 13,392.79
5. Step 5: Solve for x
   x = 13,392.79/123.12
6. Step 6: Final answer
   x = 108.78