Finding the Fourth Proportional to 78.86, 117.71 and 78.18

Step by Step Solution

1. Step 1: Write the proportion equation
   78.86 : 117.71 = 78.18 : x
2. Step 2: Convert to fraction form
   78.86/117.71 = 78.18/x
3. Step 3: Cross multiply
   78.86x = 117.71 × 78.18
4. Step 4: Simplify right side
   78.86x = 9,202.18
5. Step 5: Solve for x
   x = 9,202.18/78.86
6. Step 6: Final answer
   x = 116.70