Finding the Fourth Proportional to 1,407.30, 2,105.55 and 921.30

Step by Step Solution

1. Step 1: Write the proportion equation
   1,407.30 : 2,105.55 = 921.30 : x
2. Step 2: Convert to fraction form
   1,407.30/2,105.55 = 921.30/x
3. Step 3: Cross multiply
   1,407.30x = 2,105.55 × 921.30
4. Step 4: Simplify right side
   1,407.30x = 1,939,843.22
5. Step 5: Solve for x
   x = 1,939,843.22/1,407.30
6. Step 6: Final answer
   x = 1,378.41