Finding the Fourth Proportional to 1,369.99, 1,890.37 and 780.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,369.99 : 1,890.37 = 780.31 : x
2. Step 2: Convert to fraction form
   1,369.99/1,890.37 = 780.31/x
3. Step 3: Cross multiply
   1,369.99x = 1,890.37 × 780.31
4. Step 4: Simplify right side
   1,369.99x = 1,475,074.61
5. Step 5: Solve for x
   x = 1,475,074.61/1,369.99
6. Step 6: Final answer
   x = 1,076.70