Finding the Fourth Proportional to 1,381.40, 1,906.38 and 783.89

Step by Step Solution

1. Step 1: Write the proportion equation
   1,381.40 : 1,906.38 = 783.89 : x
2. Step 2: Convert to fraction form
   1,381.40/1,906.38 = 783.89/x
3. Step 3: Cross multiply
   1,381.40x = 1,906.38 × 783.89
4. Step 4: Simplify right side
   1,381.40x = 1,494,382.27
5. Step 5: Solve for x
   x = 1,494,382.27/1,381.40
6. Step 6: Final answer
   x = 1,081.78