Finding the Fourth Proportional to 1,388.45, 1,915.23 and 916.35

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.45 : 1,915.23 = 916.35 : x
2. Step 2: Convert to fraction form
   1,388.45/1,915.23 = 916.35/x
3. Step 3: Cross multiply
   1,388.45x = 1,915.23 × 916.35
4. Step 4: Simplify right side
   1,388.45x = 1,755,021.01
5. Step 5: Solve for x
   x = 1,755,021.01/1,388.45
6. Step 6: Final answer
   x = 1,264.01