Finding the Fourth Proportional to 1,389.83, 1,916.70 and 917.39

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.83 : 1,916.70 = 917.39 : x
2. Step 2: Convert to fraction form
   1,389.83/1,916.70 = 917.39/x
3. Step 3: Cross multiply
   1,389.83x = 1,916.70 × 917.39
4. Step 4: Simplify right side
   1,389.83x = 1,758,361.41
5. Step 5: Solve for x
   x = 1,758,361.41/1,389.83
6. Step 6: Final answer
   x = 1,265.16