Finding the Fourth Proportional to 1,287.76, 1,921.50 and 1,209.38

Step by Step Solution

1. Step 1: Write the proportion equation
   1,287.76 : 1,921.50 = 1,209.38 : x
2. Step 2: Convert to fraction form
   1,287.76/1,921.50 = 1,209.38/x
3. Step 3: Cross multiply
   1,287.76x = 1,921.50 × 1,209.38
4. Step 4: Simplify right side
   1,287.76x = 2,323,823.67
5. Step 5: Solve for x
   x = 2,323,823.67/1,287.76
6. Step 6: Final answer
   x = 1,804.55