Finding the Fourth Proportional to 2,111.78, 3,167.70 and 879.20

Step by Step Solution

1. Step 1: Write the proportion equation
   2,111.78 : 3,167.70 = 879.20 : x
2. Step 2: Convert to fraction form
   2,111.78/3,167.70 = 879.20/x
3. Step 3: Cross multiply
   2,111.78x = 3,167.70 × 879.20
4. Step 4: Simplify right side
   2,111.78x = 2,785,041.84
5. Step 5: Solve for x
   x = 2,785,041.84/2,111.78
6. Step 6: Final answer
   x = 1,318.81