Finding the Fourth Proportional to 80.78, 111.53 and 51.72

Step by Step Solution

1. Step 1: Write the proportion equation
   80.78 : 111.53 = 51.72 : x
2. Step 2: Convert to fraction form
   80.78/111.53 = 51.72/x
3. Step 3: Cross multiply
   80.78x = 111.53 × 51.72
4. Step 4: Simplify right side
   80.78x = 5,768.33
5. Step 5: Solve for x
   x = 5,768.33/80.78
6. Step 6: Final answer
   x = 71.41