Finding the Fourth Proportional to 78.72, 118.20 and 64.56

Step by Step Solution

1. Step 1: Write the proportion equation
   78.72 : 118.20 = 64.56 : x
2. Step 2: Convert to fraction form
   78.72/118.20 = 64.56/x
3. Step 3: Cross multiply
   78.72x = 118.20 × 64.56
4. Step 4: Simplify right side
   78.72x = 7,630.99
5. Step 5: Solve for x
   x = 7,630.99/78.72
6. Step 6: Final answer
   x = 96.94