Finding the Fourth Proportional to 86.69, 129.33 and 78.84

Step by Step Solution

1. Step 1: Write the proportion equation
   86.69 : 129.33 = 78.84 : x
2. Step 2: Convert to fraction form
   86.69/129.33 = 78.84/x
3. Step 3: Cross multiply
   86.69x = 129.33 × 78.84
4. Step 4: Simplify right side
   86.69x = 10,196.38
5. Step 5: Solve for x
   x = 10,196.38/86.69
6. Step 6: Final answer
   x = 117.63