Finding the Fourth Proportional to 1,378.15, 1,901.61 and 780.62

Step by Step Solution

1. Step 1: Write the proportion equation
   1,378.15 : 1,901.61 = 780.62 : x
2. Step 2: Convert to fraction form
   1,378.15/1,901.61 = 780.62/x
3. Step 3: Cross multiply
   1,378.15x = 1,901.61 × 780.62
4. Step 4: Simplify right side
   1,378.15x = 1,484,434.80
5. Step 5: Solve for x
   x = 1,484,434.80/1,378.15
6. Step 6: Final answer
   x = 1,077.12