Finding the Fourth Proportional to 1,439.28, 1,985.04 and 915.12

Step by Step Solution

1. Step 1: Write the proportion equation
   1,439.28 : 1,985.04 = 915.12 : x
2. Step 2: Convert to fraction form
   1,439.28/1,985.04 = 915.12/x
3. Step 3: Cross multiply
   1,439.28x = 1,985.04 × 915.12
4. Step 4: Simplify right side
   1,439.28x = 1,816,549.80
5. Step 5: Solve for x
   x = 1,816,549.80/1,439.28
6. Step 6: Final answer
   x = 1,262.12