Finding the Fourth Proportional to 2,087.71, 3,128.91 and 853.67

Step by Step Solution

1. Step 1: Write the proportion equation
   2,087.71 : 3,128.91 = 853.67 : x
2. Step 2: Convert to fraction form
   2,087.71/3,128.91 = 853.67/x
3. Step 3: Cross multiply
   2,087.71x = 3,128.91 × 853.67
4. Step 4: Simplify right side
   2,087.71x = 2,671,061.22
5. Step 5: Solve for x
   x = 2,671,061.22/2,087.71
6. Step 6: Final answer
   x = 1,279.42