Finding the Fourth Proportional to 78.18, 117.78 and 64.77

Step by Step Solution

1. Step 1: Write the proportion equation
   78.18 : 117.78 = 64.77 : x
2. Step 2: Convert to fraction form
   78.18/117.78 = 64.77/x
3. Step 3: Cross multiply
   78.18x = 117.78 × 64.77
4. Step 4: Simplify right side
   78.18x = 7,628.61
5. Step 5: Solve for x
   x = 7,628.61/78.18
6. Step 6: Final answer
   x = 97.58