Finding the Fourth Proportional to 102.42, 141.42 and 90.78

Step by Step Solution

1. Step 1: Write the proportion equation
   102.42 : 141.42 = 90.78 : x
2. Step 2: Convert to fraction form
   102.42/141.42 = 90.78/x
3. Step 3: Cross multiply
   102.42x = 141.42 × 90.78
4. Step 4: Simplify right side
   102.42x = 12,838.11
5. Step 5: Solve for x
   x = 12,838.11/102.42
6. Step 6: Final answer
   x = 125.35