Finding the Fourth Proportional to 1,369.90, 1,890.43 and 780.49

Step by Step Solution

1. Step 1: Write the proportion equation
   1,369.90 : 1,890.43 = 780.49 : x
2. Step 2: Convert to fraction form
   1,369.90/1,890.43 = 780.49/x
3. Step 3: Cross multiply
   1,369.90x = 1,890.43 × 780.49
4. Step 4: Simplify right side
   1,369.90x = 1,475,461.71
5. Step 5: Solve for x
   x = 1,475,461.71/1,369.90
6. Step 6: Final answer
   x = 1,077.06