Finding the Fourth Proportional to 1,078.58, 1,615.38 and 644.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,078.58 : 1,615.38 = 644.78 : x
2. Step 2: Convert to fraction form
   1,078.58/1,615.38 = 644.78/x
3. Step 3: Cross multiply
   1,078.58x = 1,615.38 × 644.78
4. Step 4: Simplify right side
   1,078.58x = 1,041,564.72
5. Step 5: Solve for x
   x = 1,041,564.72/1,078.58
6. Step 6: Final answer
   x = 965.68