Finding the Fourth Proportional to 78.78, 108.72 and 51.12

Step by Step Solution

1. Step 1: Write the proportion equation
   78.78 : 108.72 = 51.12 : x
2. Step 2: Convert to fraction form
   78.78/108.72 = 51.12/x
3. Step 3: Cross multiply
   78.78x = 108.72 × 51.12
4. Step 4: Simplify right side
   78.78x = 5,557.77
5. Step 5: Solve for x
   x = 5,557.77/78.78
6. Step 6: Final answer
   x = 70.55