Finding the Fourth Proportional to 1,128.80, 1,692.86 and 398.21

Step by Step Solution

1. Step 1: Write the proportion equation
   1,128.80 : 1,692.86 = 398.21 : x
2. Step 2: Convert to fraction form
   1,128.80/1,692.86 = 398.21/x
3. Step 3: Cross multiply
   1,128.80x = 1,692.86 × 398.21
4. Step 4: Simplify right side
   1,128.80x = 674,111.91
5. Step 5: Solve for x
   x = 674,111.91/1,128.80
6. Step 6: Final answer
   x = 597.19