Finding the Fourth Proportional to 1,339.28, 2,006.72 and 1,288.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,339.28 : 2,006.72 = 1,288.72 : x
2. Step 2: Convert to fraction form
   1,339.28/2,006.72 = 1,288.72/x
3. Step 3: Cross multiply
   1,339.28x = 2,006.72 × 1,288.72
4. Step 4: Simplify right side
   1,339.28x = 2,586,100.20
5. Step 5: Solve for x
   x = 2,586,100.20/1,339.28
6. Step 6: Final answer
   x = 1,930.96