Finding the Fourth Proportional to 2,085.90, 3,129.21 and 853.98

Step by Step Solution

1. Step 1: Write the proportion equation
   2,085.90 : 3,129.21 = 853.98 : x
2. Step 2: Convert to fraction form
   2,085.90/3,129.21 = 853.98/x
3. Step 3: Cross multiply
   2,085.90x = 3,129.21 × 853.98
4. Step 4: Simplify right side
   2,085.90x = 2,672,282.76
5. Step 5: Solve for x
   x = 2,672,282.76/2,085.90
6. Step 6: Final answer
   x = 1,281.12