Finding the Fourth Proportional to 90.42, 124.74 and 81.31

Step by Step Solution

1. Step 1: Write the proportion equation
   90.42 : 124.74 = 81.31 : x
2. Step 2: Convert to fraction form
   90.42/124.74 = 81.31/x
3. Step 3: Cross multiply
   90.42x = 124.74 × 81.31
4. Step 4: Simplify right side
   90.42x = 10,142.61
5. Step 5: Solve for x
   x = 10,142.61/90.42
6. Step 6: Final answer
   x = 112.17