Finding the Fourth Proportional to 1,578.38, 2,178.17 and 870.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,578.38 : 2,178.17 = 870.20 : x
2. Step 2: Convert to fraction form
   1,578.38/2,178.17 = 870.20/x
3. Step 3: Cross multiply
   1,578.38x = 2,178.17 × 870.20
4. Step 4: Simplify right side
   1,578.38x = 1,895,443.53
5. Step 5: Solve for x
   x = 1,895,443.53/1,578.38
6. Step 6: Final answer
   x = 1,200.88