Finding the Fourth Proportional to 1,287.71, 1,923.72 and 821.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,287.71 : 1,923.72 = 821.78 : x
2. Step 2: Convert to fraction form
   1,287.71/1,923.72 = 821.78/x
3. Step 3: Cross multiply
   1,287.71x = 1,923.72 × 821.78
4. Step 4: Simplify right side
   1,287.71x = 1,580,865.00
5. Step 5: Solve for x
   x = 1,580,865.00/1,287.71
6. Step 6: Final answer
   x = 1,227.66