Finding the Fourth Proportional to 1,638.24, 2,260.72 and 939.60

Step by Step Solution

1. Step 1: Write the proportion equation
   1,638.24 : 2,260.72 = 939.60 : x
2. Step 2: Convert to fraction form
   1,638.24/2,260.72 = 939.60/x
3. Step 3: Cross multiply
   1,638.24x = 2,260.72 × 939.60
4. Step 4: Simplify right side
   1,638.24x = 2,124,172.51
5. Step 5: Solve for x
   x = 2,124,172.51/1,638.24
6. Step 6: Final answer
   x = 1,296.62