Finding the Fourth Proportional to 2,105.99, 3,145.65 and 1,638.91

Step by Step Solution

1. Step 1: Write the proportion equation
   2,105.99 : 3,145.65 = 1,638.91 : x
2. Step 2: Convert to fraction form
   2,105.99/3,145.65 = 1,638.91/x
3. Step 3: Cross multiply
   2,105.99x = 3,145.65 × 1,638.91
4. Step 4: Simplify right side
   2,105.99x = 5,155,437.24
5. Step 5: Solve for x
   x = 5,155,437.24/2,105.99
6. Step 6: Final answer
   x = 2,447.99