Finding the Fourth Proportional to 1,387.92, 1,915.95 and 916.10

Step by Step Solution

1. Step 1: Write the proportion equation
   1,387.92 : 1,915.95 = 916.10 : x
2. Step 2: Convert to fraction form
   1,387.92/1,915.95 = 916.10/x
3. Step 3: Cross multiply
   1,387.92x = 1,915.95 × 916.10
4. Step 4: Simplify right side
   1,387.92x = 1,755,192.22
5. Step 5: Solve for x
   x = 1,755,192.22/1,387.92
6. Step 6: Final answer
   x = 1,264.62