Finding the Fourth Proportional to 1,059.78, 1,462.40 and 640.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,059.78 : 1,462.40 = 640.31 : x
2. Step 2: Convert to fraction form
   1,059.78/1,462.40 = 640.31/x
3. Step 3: Cross multiply
   1,059.78x = 1,462.40 × 640.31
4. Step 4: Simplify right side
   1,059.78x = 936,384.83
5. Step 5: Solve for x
   x = 936,384.83/1,059.78
6. Step 6: Final answer
   x = 883.56