Finding the Fourth Proportional to 1,339.65, 1,848.56 and 780.21

Step by Step Solution

1. Step 1: Write the proportion equation
   1,339.65 : 1,848.56 = 780.21 : x
2. Step 2: Convert to fraction form
   1,339.65/1,848.56 = 780.21/x
3. Step 3: Cross multiply
   1,339.65x = 1,848.56 × 780.21
4. Step 4: Simplify right side
   1,339.65x = 1,442,261.10
5. Step 5: Solve for x
   x = 1,442,261.10/1,339.65
6. Step 6: Final answer
   x = 1,076.60