Finding the Fourth Proportional to 1,086.72, 1,499.60 and 620.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,086.72 : 1,499.60 = 620.80 : x
2. Step 2: Convert to fraction form
   1,086.72/1,499.60 = 620.80/x
3. Step 3: Cross multiply
   1,086.72x = 1,499.60 × 620.80
4. Step 4: Simplify right side
   1,086.72x = 930,951.68
5. Step 5: Solve for x
   x = 930,951.68/1,086.72
6. Step 6: Final answer
   x = 856.66