Finding the Fourth Proportional to 1,390.32, 1,921.20 and 996.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.32 : 1,921.20 = 996.72 : x
2. Step 2: Convert to fraction form
   1,390.32/1,921.20 = 996.72/x
3. Step 3: Cross multiply
   1,390.32x = 1,921.20 × 996.72
4. Step 4: Simplify right side
   1,390.32x = 1,914,898.46
5. Step 5: Solve for x
   x = 1,914,898.46/1,390.32
6. Step 6: Final answer
   x = 1,377.31