Finding the Fourth Proportional to 86.18, 129.28 and 42.86

Step by Step Solution

1. Step 1: Write the proportion equation
   86.18 : 129.28 = 42.86 : x
2. Step 2: Convert to fraction form
   86.18/129.28 = 42.86/x
3. Step 3: Cross multiply
   86.18x = 129.28 × 42.86
4. Step 4: Simplify right side
   86.18x = 5,540.94
5. Step 5: Solve for x
   x = 5,540.94/86.18
6. Step 6: Final answer
   x = 64.29