Finding the Fourth Proportional to 1,019.20, 1,406.61 and 620.88

Step by Step Solution

1. Step 1: Write the proportion equation
   1,019.20 : 1,406.61 = 620.88 : x
2. Step 2: Convert to fraction form
   1,019.20/1,406.61 = 620.88/x
3. Step 3: Cross multiply
   1,019.20x = 1,406.61 × 620.88
4. Step 4: Simplify right side
   1,019.20x = 873,336.02
5. Step 5: Solve for x
   x = 873,336.02/1,019.20
6. Step 6: Final answer
   x = 856.88