Finding the Fourth Proportional to 1,389.28, 1,916.16 and 922.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.28 : 1,916.16 = 922.72 : x
2. Step 2: Convert to fraction form
   1,389.28/1,916.16 = 922.72/x
3. Step 3: Cross multiply
   1,389.28x = 1,916.16 × 922.72
4. Step 4: Simplify right side
   1,389.28x = 1,768,079.16
5. Step 5: Solve for x
   x = 1,768,079.16/1,389.28
6. Step 6: Final answer
   x = 1,272.66