Finding the Fourth Proportional to 2,145.98, 3,218.76 and 686.18

Step by Step Solution

1. Step 1: Write the proportion equation
   2,145.98 : 3,218.76 = 686.18 : x
2. Step 2: Convert to fraction form
   2,145.98/3,218.76 = 686.18/x
3. Step 3: Cross multiply
   2,145.98x = 3,218.76 × 686.18
4. Step 4: Simplify right side
   2,145.98x = 2,208,648.74
5. Step 5: Solve for x
   x = 2,208,648.74/2,145.98
6. Step 6: Final answer
   x = 1,029.20