Finding the Fourth Proportional to 1,086.80, 1,629.73 and 419.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,086.80 : 1,629.73 = 419.31 : x
2. Step 2: Convert to fraction form
   1,086.80/1,629.73 = 419.31/x
3. Step 3: Cross multiply
   1,086.80x = 1,629.73 × 419.31
4. Step 4: Simplify right side
   1,086.80x = 683,362.61
5. Step 5: Solve for x
   x = 683,362.61/1,086.80
6. Step 6: Final answer
   x = 628.79