Finding the Fourth Proportional to 2,187.67, 3,279.89 and 1,321.78

Step by Step Solution

1. Step 1: Write the proportion equation
   2,187.67 : 3,279.89 = 1,321.78 : x
2. Step 2: Convert to fraction form
   2,187.67/3,279.89 = 1,321.78/x
3. Step 3: Cross multiply
   2,187.67x = 3,279.89 × 1,321.78
4. Step 4: Simplify right side
   2,187.67x = 4,335,286.40
5. Step 5: Solve for x
   x = 4,335,286.40/2,187.67
6. Step 6: Final answer
   x = 1,981.69