Finding the Fourth Proportional to 78.93, 109.05 and 64.56

Step by Step Solution

1. Step 1: Write the proportion equation
   78.93 : 109.05 = 64.56 : x
2. Step 2: Convert to fraction form
   78.93/109.05 = 64.56/x
3. Step 3: Cross multiply
   78.93x = 109.05 × 64.56
4. Step 4: Simplify right side
   78.93x = 7,040.27
5. Step 5: Solve for x
   x = 7,040.27/78.93
6. Step 6: Final answer
   x = 89.20