Finding the Fourth Proportional to 1,018.38, 1,405.43 and 620.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,018.38 : 1,405.43 = 620.31 : x
2. Step 2: Convert to fraction form
   1,018.38/1,405.43 = 620.31/x
3. Step 3: Cross multiply
   1,018.38x = 1,405.43 × 620.31
4. Step 4: Simplify right side
   1,018.38x = 871,799.18
5. Step 5: Solve for x
   x = 871,799.18/1,018.38
6. Step 6: Final answer
   x = 856.06