Finding the Fourth Proportional to 103.61, 155.15 and 78.09

Step by Step Solution

1. Step 1: Write the proportion equation
   103.61 : 155.15 = 78.09 : x
2. Step 2: Convert to fraction form
   103.61/155.15 = 78.09/x
3. Step 3: Cross multiply
   103.61x = 155.15 × 78.09
4. Step 4: Simplify right side
   103.61x = 12,115.27
5. Step 5: Solve for x
   x = 12,115.27/103.61
6. Step 6: Final answer
   x = 116.94