Finding the Fourth Proportional to 80.87, 111.56 and 51.78

Step by Step Solution

1. Step 1: Write the proportion equation
   80.87 : 111.56 = 51.78 : x
2. Step 2: Convert to fraction form
   80.87/111.56 = 51.78/x
3. Step 3: Cross multiply
   80.87x = 111.56 × 51.78
4. Step 4: Simplify right side
   80.87x = 5,776.32
5. Step 5: Solve for x
   x = 5,776.32/80.87
6. Step 6: Final answer
   x = 71.42