Finding the Fourth Proportional to 1,388.72, 1,916.17 and 891.29

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.72 : 1,916.17 = 891.29 : x
2. Step 2: Convert to fraction form
   1,388.72/1,916.17 = 891.29/x
3. Step 3: Cross multiply
   1,388.72x = 1,916.17 × 891.29
4. Step 4: Simplify right side
   1,388.72x = 1,707,865.72
5. Step 5: Solve for x
   x = 1,707,865.72/1,388.72
6. Step 6: Final answer
   x = 1,229.81