Finding the Fourth Proportional to 2,071.28, 2,858.31 and 1,139.78

Step by Step Solution

1. Step 1: Write the proportion equation
   2,071.28 : 2,858.31 = 1,139.78 : x
2. Step 2: Convert to fraction form
   2,071.28/2,858.31 = 1,139.78/x
3. Step 3: Cross multiply
   2,071.28x = 2,858.31 × 1,139.78
4. Step 4: Simplify right side
   2,071.28x = 3,257,844.57
5. Step 5: Solve for x
   x = 3,257,844.57/2,071.28
6. Step 6: Final answer
   x = 1,572.87