Finding the Fourth Proportional to 78.72, 118.14 and 67.20

Step by Step Solution

1. Step 1: Write the proportion equation
   78.72 : 118.14 = 67.20 : x
2. Step 2: Convert to fraction form
   78.72/118.14 = 67.20/x
3. Step 3: Cross multiply
   78.72x = 118.14 × 67.20
4. Step 4: Simplify right side
   78.72x = 7,939.01
5. Step 5: Solve for x
   x = 7,939.01/78.72
6. Step 6: Final answer
   x = 100.85