Finding the Fourth Proportional to 1,578.81, 2,178.56 and 915.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,578.81 : 2,178.56 = 915.57 : x
2. Step 2: Convert to fraction form
   1,578.81/2,178.56 = 915.57/x
3. Step 3: Cross multiply
   1,578.81x = 2,178.56 × 915.57
4. Step 4: Simplify right side
   1,578.81x = 1,994,624.18
5. Step 5: Solve for x
   x = 1,994,624.18/1,578.81
6. Step 6: Final answer
   x = 1,263.37