Finding the Fourth Proportional to 1,369.91, 1,890.38 and 780.43

Step by Step Solution

1. Step 1: Write the proportion equation
   1,369.91 : 1,890.38 = 780.43 : x
2. Step 2: Convert to fraction form
   1,369.91/1,890.38 = 780.43/x
3. Step 3: Cross multiply
   1,369.91x = 1,890.38 × 780.43
4. Step 4: Simplify right side
   1,369.91x = 1,475,295.91
5. Step 5: Solve for x
   x = 1,475,295.91/1,369.91
6. Step 6: Final answer
   x = 1,076.93