Finding the Fourth Proportional to 2,087.37, 3,128.69 and 853.20

Step by Step Solution

1. Step 1: Write the proportion equation
   2,087.37 : 3,128.69 = 853.20 : x
2. Step 2: Convert to fraction form
   2,087.37/3,128.69 = 853.20/x
3. Step 3: Cross multiply
   2,087.37x = 3,128.69 × 853.20
4. Step 4: Simplify right side
   2,087.37x = 2,669,400.44
5. Step 5: Solve for x
   x = 2,669,400.44/2,087.37
6. Step 6: Final answer
   x = 1,278.83