Finding the Fourth Proportional to 1,388.96, 1,915.92 and 916.85

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.96 : 1,915.92 = 916.85 : x
2. Step 2: Convert to fraction form
   1,388.96/1,915.92 = 916.85/x
3. Step 3: Cross multiply
   1,388.96x = 1,915.92 × 916.85
4. Step 4: Simplify right side
   1,388.96x = 1,756,616.04
5. Step 5: Solve for x
   x = 1,756,616.04/1,388.96
6. Step 6: Final answer
   x = 1,264.70