Finding the Fourth Proportional to 86.78, 118.16 and 86.51

Step by Step Solution

1. Step 1: Write the proportion equation
   86.78 : 118.16 = 86.51 : x
2. Step 2: Convert to fraction form
   86.78/118.16 = 86.51/x
3. Step 3: Cross multiply
   86.78x = 118.16 × 86.51
4. Step 4: Simplify right side
   86.78x = 10,221.88
5. Step 5: Solve for x
   x = 10,221.88/86.78
6. Step 6: Final answer
   x = 117.79