Finding the Fourth Proportional to 102.78, 141.83 and 56.15

Step by Step Solution

1. Step 1: Write the proportion equation
   102.78 : 141.83 = 56.15 : x
2. Step 2: Convert to fraction form
   102.78/141.83 = 56.15/x
3. Step 3: Cross multiply
   102.78x = 141.83 × 56.15
4. Step 4: Simplify right side
   102.78x = 7,964.22
5. Step 5: Solve for x
   x = 7,964.22/102.78
6. Step 6: Final answer
   x = 77.49