Finding the Fourth Proportional to 2,071.20, 2,858.10 and 1,139.76

Step by Step Solution

1. Step 1: Write the proportion equation
   2,071.20 : 2,858.10 = 1,139.76 : x
2. Step 2: Convert to fraction form
   2,071.20/2,858.10 = 1,139.76/x
3. Step 3: Cross multiply
   2,071.20x = 2,858.10 × 1,139.76
4. Step 4: Simplify right side
   2,071.20x = 3,257,548.06
5. Step 5: Solve for x
   x = 3,257,548.06/2,071.20
6. Step 6: Final answer
   x = 1,572.78