Finding the Fourth Proportional to 1,398.57, 1,930.78 and 980.21

Step by Step Solution

1. Step 1: Write the proportion equation
   1,398.57 : 1,930.78 = 980.21 : x
2. Step 2: Convert to fraction form
   1,398.57/1,930.78 = 980.21/x
3. Step 3: Cross multiply
   1,398.57x = 1,930.78 × 980.21
4. Step 4: Simplify right side
   1,398.57x = 1,892,560.21
5. Step 5: Solve for x
   x = 1,892,560.21/1,398.57
6. Step 6: Final answer
   x = 1,353.21