Finding the Fourth Proportional to 78.72, 108.72 and 73.20

Step by Step Solution

1. Step 1: Write the proportion equation
   78.72 : 108.72 = 73.20 : x
2. Step 2: Convert to fraction form
   78.72/108.72 = 73.20/x
3. Step 3: Cross multiply
   78.72x = 108.72 × 73.20
4. Step 4: Simplify right side
   78.72x = 7,958.30
5. Step 5: Solve for x
   x = 7,958.30/78.72
6. Step 6: Final answer
   x = 101.10