Finding the Fourth Proportional to 1,391.55, 1,919.21 and 998.79

Step by Step Solution

1. Step 1: Write the proportion equation
   1,391.55 : 1,919.21 = 998.79 : x
2. Step 2: Convert to fraction form
   1,391.55/1,919.21 = 998.79/x
3. Step 3: Cross multiply
   1,391.55x = 1,919.21 × 998.79
4. Step 4: Simplify right side
   1,391.55x = 1,916,882.76
5. Step 5: Solve for x
   x = 1,916,882.76/1,391.55
6. Step 6: Final answer
   x = 1,377.52