Finding the Fourth Proportional to 109.05, 163.32 and 78.60

Step by Step Solution

1. Step 1: Write the proportion equation
   109.05 : 163.32 = 78.60 : x
2. Step 2: Convert to fraction form
   109.05/163.32 = 78.60/x
3. Step 3: Cross multiply
   109.05x = 163.32 × 78.60
4. Step 4: Simplify right side
   109.05x = 12,837.27
5. Step 5: Solve for x
   x = 12,837.27/109.05
6. Step 6: Final answer
   x = 117.72