Finding the Fourth Proportional to 2,085.67, 3,128.70 and 853.06

Step by Step Solution

1. Step 1: Write the proportion equation
   2,085.67 : 3,128.70 = 853.06 : x
2. Step 2: Convert to fraction form
   2,085.67/3,128.70 = 853.06/x
3. Step 3: Cross multiply
   2,085.67x = 3,128.70 × 853.06
4. Step 4: Simplify right side
   2,085.67x = 2,668,968.82
5. Step 5: Solve for x
   x = 2,668,968.82/2,085.67
6. Step 6: Final answer
   x = 1,279.67