Finding the Fourth Proportional to 1,439.32, 2,158.29 and 780.15

Step by Step Solution

1. Step 1: Write the proportion equation
   1,439.32 : 2,158.29 = 780.15 : x
2. Step 2: Convert to fraction form
   1,439.32/2,158.29 = 780.15/x
3. Step 3: Cross multiply
   1,439.32x = 2,158.29 × 780.15
4. Step 4: Simplify right side
   1,439.32x = 1,683,789.94
5. Step 5: Solve for x
   x = 1,683,789.94/1,439.32
6. Step 6: Final answer
   x = 1,169.85