Finding the Fourth Proportional to 1,439.64, 1,986.12 and 915.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,439.64 : 1,986.12 = 915.57 : x
2. Step 2: Convert to fraction form
   1,439.64/1,986.12 = 915.57/x
3. Step 3: Cross multiply
   1,439.64x = 1,986.12 × 915.57
4. Step 4: Simplify right side
   1,439.64x = 1,818,431.89
5. Step 5: Solve for x
   x = 1,818,431.89/1,439.64
6. Step 6: Final answer
   x = 1,263.12