Finding the Fourth Proportional to 2,086.38, 3,129.60 and 853.50

Step by Step Solution

1. Step 1: Write the proportion equation
   2,086.38 : 3,129.60 = 853.50 : x
2. Step 2: Convert to fraction form
   2,086.38/3,129.60 = 853.50/x
3. Step 3: Cross multiply
   2,086.38x = 3,129.60 × 853.50
4. Step 4: Simplify right side
   2,086.38x = 2,671,113.60
5. Step 5: Solve for x
   x = 2,671,113.60/2,086.38
6. Step 6: Final answer
   x = 1,280.26