Finding the Fourth Proportional to 78.69, 118.17 and 76.86

Step by Step Solution

1. Step 1: Write the proportion equation
   78.69 : 118.17 = 76.86 : x
2. Step 2: Convert to fraction form
   78.69/118.17 = 76.86/x
3. Step 3: Cross multiply
   78.69x = 118.17 × 76.86
4. Step 4: Simplify right side
   78.69x = 9,082.55
5. Step 5: Solve for x
   x = 9,082.55/78.69
6. Step 6: Final answer
   x = 115.42