Finding the Fourth Proportional to 2,085.12, 3,129.11 and 1,111.91

Step by Step Solution

1. Step 1: Write the proportion equation
   2,085.12 : 3,129.11 = 1,111.91 : x
2. Step 2: Convert to fraction form
   2,085.12/3,129.11 = 1,111.91/x
3. Step 3: Cross multiply
   2,085.12x = 3,129.11 × 1,111.91
4. Step 4: Simplify right side
   2,085.12x = 3,479,267.50
5. Step 5: Solve for x
   x = 3,479,267.50/2,085.12
6. Step 6: Final answer
   x = 1,668.62