Finding the Fourth Proportional to 1,380.29, 1,904.64 and 782.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,380.29 : 1,904.64 = 782.78 : x
2. Step 2: Convert to fraction form
   1,380.29/1,904.64 = 782.78/x
3. Step 3: Cross multiply
   1,380.29x = 1,904.64 × 782.78
4. Step 4: Simplify right side
   1,380.29x = 1,490,914.10
5. Step 5: Solve for x
   x = 1,490,914.10/1,380.29
6. Step 6: Final answer
   x = 1,080.15