Finding the Fourth Proportional to 1,389.81, 1,916.06 and 891.58

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.81 : 1,916.06 = 891.58 : x
2. Step 2: Convert to fraction form
   1,389.81/1,916.06 = 891.58/x
3. Step 3: Cross multiply
   1,389.81x = 1,916.06 × 891.58
4. Step 4: Simplify right side
   1,389.81x = 1,708,324.27
5. Step 5: Solve for x
   x = 1,708,324.27/1,389.81
6. Step 6: Final answer
   x = 1,229.18