Finding the Fourth Proportional to 1,371.20, 1,891.79 and 781.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,371.20 : 1,891.79 = 781.31 : x
2. Step 2: Convert to fraction form
   1,371.20/1,891.79 = 781.31/x
3. Step 3: Cross multiply
   1,371.20x = 1,891.79 × 781.31
4. Step 4: Simplify right side
   1,371.20x = 1,478,070.54
5. Step 5: Solve for x
   x = 1,478,070.54/1,371.20
6. Step 6: Final answer
   x = 1,077.94