Finding the Fourth Proportional to 1,387.96, 1,916.12 and 916.18

Step by Step Solution

1. Step 1: Write the proportion equation
   1,387.96 : 1,916.12 = 916.18 : x
2. Step 2: Convert to fraction form
   1,387.96/1,916.12 = 916.18/x
3. Step 3: Cross multiply
   1,387.96x = 1,916.12 × 916.18
4. Step 4: Simplify right side
   1,387.96x = 1,755,510.82
5. Step 5: Solve for x
   x = 1,755,510.82/1,387.96
6. Step 6: Final answer
   x = 1,264.81