Finding the Fourth Proportional to 1,288.55, 1,933.43 and 639.27

Step by Step Solution

1. Step 1: Write the proportion equation
   1,288.55 : 1,933.43 = 639.27 : x
2. Step 2: Convert to fraction form
   1,288.55/1,933.43 = 639.27/x
3. Step 3: Cross multiply
   1,288.55x = 1,933.43 × 639.27
4. Step 4: Simplify right side
   1,288.55x = 1,235,980.60
5. Step 5: Solve for x
   x = 1,235,980.60/1,288.55
6. Step 6: Final answer
   x = 959.20