Finding the Fourth Proportional to 1,380.89, 1,905.19 and 783.28

Step by Step Solution

1. Step 1: Write the proportion equation
   1,380.89 : 1,905.19 = 783.28 : x
2. Step 2: Convert to fraction form
   1,380.89/1,905.19 = 783.28/x
3. Step 3: Cross multiply
   1,380.89x = 1,905.19 × 783.28
4. Step 4: Simplify right side
   1,380.89x = 1,492,295.82
5. Step 5: Solve for x
   x = 1,492,295.82/1,380.89
6. Step 6: Final answer
   x = 1,080.68