Finding the Fourth Proportional to 1,390.50, 1,918.89 and 769.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.50 : 1,918.89 = 769.50 : x
2. Step 2: Convert to fraction form
   1,390.50/1,918.89 = 769.50/x
3. Step 3: Cross multiply
   1,390.50x = 1,918.89 × 769.50
4. Step 4: Simplify right side
   1,390.50x = 1,476,585.86
5. Step 5: Solve for x
   x = 1,476,585.86/1,390.50
6. Step 6: Final answer
   x = 1,061.91