Finding the Fourth Proportional to 1,439.40, 1,985.67 and 915.60

Step by Step Solution

1. Step 1: Write the proportion equation
   1,439.40 : 1,985.67 = 915.60 : x
2. Step 2: Convert to fraction form
   1,439.40/1,985.67 = 915.60/x
3. Step 3: Cross multiply
   1,439.40x = 1,985.67 × 915.60
4. Step 4: Simplify right side
   1,439.40x = 1,818,079.45
5. Step 5: Solve for x
   x = 1,818,079.45/1,439.40
6. Step 6: Final answer
   x = 1,263.08