Finding the Fourth Proportional to 1,086.38, 1,628.61 and 427.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,086.38 : 1,628.61 = 427.78 : x
2. Step 2: Convert to fraction form
   1,086.38/1,628.61 = 427.78/x
3. Step 3: Cross multiply
   1,086.38x = 1,628.61 × 427.78
4. Step 4: Simplify right side
   1,086.38x = 696,687.22
5. Step 5: Solve for x
   x = 696,687.22/1,086.38
6. Step 6: Final answer
   x = 641.29