Finding the Fourth Proportional to 1,380.26, 1,904.80 and 782.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,380.26 : 1,904.80 = 782.78 : x
2. Step 2: Convert to fraction form
   1,380.26/1,904.80 = 782.78/x
3. Step 3: Cross multiply
   1,380.26x = 1,904.80 × 782.78
4. Step 4: Simplify right side
   1,380.26x = 1,491,039.34
5. Step 5: Solve for x
   x = 1,491,039.34/1,380.26
6. Step 6: Final answer
   x = 1,080.26