Finding the Fourth Proportional to 1,390.84, 1,916.27 and 917.89

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.84 : 1,916.27 = 917.89 : x
2. Step 2: Convert to fraction form
   1,390.84/1,916.27 = 917.89/x
3. Step 3: Cross multiply
   1,390.84x = 1,916.27 × 917.89
4. Step 4: Simplify right side
   1,390.84x = 1,758,920.48
5. Step 5: Solve for x
   x = 1,758,920.48/1,390.84
6. Step 6: Final answer
   x = 1,264.65