Finding the Fourth Proportional to 78.86, 118.72 and 71.80

Step by Step Solution

1. Step 1: Write the proportion equation
   78.86 : 118.72 = 71.80 : x
2. Step 2: Convert to fraction form
   78.86/118.72 = 71.80/x
3. Step 3: Cross multiply
   78.86x = 118.72 × 71.80
4. Step 4: Simplify right side
   78.86x = 8,524.10
5. Step 5: Solve for x
   x = 8,524.10/78.86
6. Step 6: Final answer
   x = 108.09