Finding the Fourth Proportional to 1,380.17, 1,904.60 and 782.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,380.17 : 1,904.60 = 782.72 : x
2. Step 2: Convert to fraction form
   1,380.17/1,904.60 = 782.72/x
3. Step 3: Cross multiply
   1,380.17x = 1,904.60 × 782.72
4. Step 4: Simplify right side
   1,380.17x = 1,490,755.08
5. Step 5: Solve for x
   x = 1,490,755.08/1,380.17
6. Step 6: Final answer
   x = 1,080.12