Finding the Fourth Proportional to 1,019.38, 1,406.81 and 621.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,019.38 : 1,406.81 = 621.31 : x
2. Step 2: Convert to fraction form
   1,019.38/1,406.81 = 621.31/x
3. Step 3: Cross multiply
   1,019.38x = 1,406.81 × 621.31
4. Step 4: Simplify right side
   1,019.38x = 874,065.12
5. Step 5: Solve for x
   x = 874,065.12/1,019.38
6. Step 6: Final answer
   x = 857.45