Finding the Fourth Proportional to 1,370.72, 1,891.61 and 781.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,370.72 : 1,891.61 = 781.31 : x
2. Step 2: Convert to fraction form
   1,370.72/1,891.61 = 781.31/x
3. Step 3: Cross multiply
   1,370.72x = 1,891.61 × 781.31
4. Step 4: Simplify right side
   1,370.72x = 1,477,933.81
5. Step 5: Solve for x
   x = 1,477,933.81/1,370.72
6. Step 6: Final answer
   x = 1,078.22