Finding the Fourth Proportional to 2,086.20, 3,131.70 and 1,265.40

Step by Step Solution

1. Step 1: Write the proportion equation
   2,086.20 : 3,131.70 = 1,265.40 : x
2. Step 2: Convert to fraction form
   2,086.20/3,131.70 = 1,265.40/x
3. Step 3: Cross multiply
   2,086.20x = 3,131.70 × 1,265.40
4. Step 4: Simplify right side
   2,086.20x = 3,962,853.18
5. Step 5: Solve for x
   x = 3,962,853.18/2,086.20
6. Step 6: Final answer
   x = 1,899.56