Finding the Fourth Proportional to 1,393.91, 1,923.86 and 921.83

Step by Step Solution

1. Step 1: Write the proportion equation
   1,393.91 : 1,923.86 = 921.83 : x
2. Step 2: Convert to fraction form
   1,393.91/1,923.86 = 921.83/x
3. Step 3: Cross multiply
   1,393.91x = 1,923.86 × 921.83
4. Step 4: Simplify right side
   1,393.91x = 1,773,471.76
5. Step 5: Solve for x
   x = 1,773,471.76/1,393.91
6. Step 6: Final answer
   x = 1,272.30