Finding the Fourth Proportional to 1,388.45, 1,916.39 and 916.43

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.45 : 1,916.39 = 916.43 : x
2. Step 2: Convert to fraction form
   1,388.45/1,916.39 = 916.43/x
3. Step 3: Cross multiply
   1,388.45x = 1,916.39 × 916.43
4. Step 4: Simplify right side
   1,388.45x = 1,756,223.12
5. Step 5: Solve for x
   x = 1,756,223.12/1,388.45
6. Step 6: Final answer
   x = 1,264.88