Finding the Fourth Proportional to 2,275.40, 3,139.42 and 1,391.12

Step by Step Solution

1. Step 1: Write the proportion equation
   2,275.40 : 3,139.42 = 1,391.12 : x
2. Step 2: Convert to fraction form
   2,275.40/3,139.42 = 1,391.12/x
3. Step 3: Cross multiply
   2,275.40x = 3,139.42 × 1,391.12
4. Step 4: Simplify right side
   2,275.40x = 4,367,309.95
5. Step 5: Solve for x
   x = 4,367,309.95/2,275.40
6. Step 6: Final answer
   x = 1,919.36