Finding the Fourth Proportional to 124.72, 172.22 and 78.15

Step by Step Solution

1. Step 1: Write the proportion equation
   124.72 : 172.22 = 78.15 : x
2. Step 2: Convert to fraction form
   124.72/172.22 = 78.15/x
3. Step 3: Cross multiply
   124.72x = 172.22 × 78.15
4. Step 4: Simplify right side
   124.72x = 13,458.72
5. Step 5: Solve for x
   x = 13,458.72/124.72
6. Step 6: Final answer
   x = 107.91