Finding the Fourth Proportional to 121.69, 167.89 and 78.02

Step by Step Solution

1. Step 1: Write the proportion equation
   121.69 : 167.89 = 78.02 : x
2. Step 2: Convert to fraction form
   121.69/167.89 = 78.02/x
3. Step 3: Cross multiply
   121.69x = 167.89 × 78.02
4. Step 4: Simplify right side
   121.69x = 13,098.78
5. Step 5: Solve for x
   x = 13,098.78/121.69
6. Step 6: Final answer
   x = 107.64