Finding the Fourth Proportional to 1,339.80, 1,848.86 and 780.28

Step by Step Solution

1. Step 1: Write the proportion equation
   1,339.80 : 1,848.86 = 780.28 : x
2. Step 2: Convert to fraction form
   1,339.80/1,848.86 = 780.28/x
3. Step 3: Cross multiply
   1,339.80x = 1,848.86 × 780.28
4. Step 4: Simplify right side
   1,339.80x = 1,442,628.48
5. Step 5: Solve for x
   x = 1,442,628.48/1,339.80
6. Step 6: Final answer
   x = 1,076.75