Finding the Fourth Proportional to 1,578.71, 2,178.56 and 870.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,578.71 : 2,178.56 = 870.55 : x
2. Step 2: Convert to fraction form
   1,578.71/2,178.56 = 870.55/x
3. Step 3: Cross multiply
   1,578.71x = 2,178.56 × 870.55
4. Step 4: Simplify right side
   1,578.71x = 1,896,545.41
5. Step 5: Solve for x
   x = 1,896,545.41/1,578.71
6. Step 6: Final answer
   x = 1,201.33