Finding the Fourth Proportional to 102.78, 141.72 and 98.76

Step by Step Solution

1. Step 1: Write the proportion equation
   102.78 : 141.72 = 98.76 : x
2. Step 2: Convert to fraction form
   102.78/141.72 = 98.76/x
3. Step 3: Cross multiply
   102.78x = 141.72 × 98.76
4. Step 4: Simplify right side
   102.78x = 13,996.27
5. Step 5: Solve for x
   x = 13,996.27/102.78
6. Step 6: Final answer
   x = 136.18