Finding the Fourth Proportional to 80.78, 111.50 and 51.35

Step by Step Solution

1. Step 1: Write the proportion equation
   80.78 : 111.50 = 51.35 : x
2. Step 2: Convert to fraction form
   80.78/111.50 = 51.35/x
3. Step 3: Cross multiply
   80.78x = 111.50 × 51.35
4. Step 4: Simplify right side
   80.78x = 5,724.71
5. Step 5: Solve for x
   x = 5,724.71/80.78
6. Step 6: Final answer
   x = 70.87