Finding the Fourth Proportional to 1,578.72, 2,178.57 and 915.12

Step by Step Solution

1. Step 1: Write the proportion equation
   1,578.72 : 2,178.57 = 915.12 : x
2. Step 2: Convert to fraction form
   1,578.72/2,178.57 = 915.12/x
3. Step 3: Cross multiply
   1,578.72x = 2,178.57 × 915.12
4. Step 4: Simplify right side
   1,578.72x = 1,993,652.98
5. Step 5: Solve for x
   x = 1,993,652.98/1,578.72
6. Step 6: Final answer
   x = 1,262.83