Finding the Fourth Proportional to 78.62, 108.42 and 64.72

Step by Step Solution

1. Step 1: Write the proportion equation
   78.62 : 108.42 = 64.72 : x
2. Step 2: Convert to fraction form
   78.62/108.42 = 64.72/x
3. Step 3: Cross multiply
   78.62x = 108.42 × 64.72
4. Step 4: Simplify right side
   78.62x = 7,016.67
5. Step 5: Solve for x
   x = 7,016.67/78.62
6. Step 6: Final answer
   x = 89.25