Finding the Fourth Proportional to 1,393.78, 1,922.70 and 928.12

Step by Step Solution

1. Step 1: Write the proportion equation
   1,393.78 : 1,922.70 = 928.12 : x
2. Step 2: Convert to fraction form
   1,393.78/1,922.70 = 928.12/x
3. Step 3: Cross multiply
   1,393.78x = 1,922.70 × 928.12
4. Step 4: Simplify right side
   1,393.78x = 1,784,496.32
5. Step 5: Solve for x
   x = 1,784,496.32/1,393.78
6. Step 6: Final answer
   x = 1,280.33