Finding the Fourth Proportional to 1,561.30, 2,155.39 and 1,206.43

Step by Step Solution

1. Step 1: Write the proportion equation
   1,561.30 : 2,155.39 = 1,206.43 : x
2. Step 2: Convert to fraction form
   1,561.30/2,155.39 = 1,206.43/x
3. Step 3: Cross multiply
   1,561.30x = 2,155.39 × 1,206.43
4. Step 4: Simplify right side
   1,561.30x = 2,600,327.16
5. Step 5: Solve for x
   x = 2,600,327.16/1,561.30
6. Step 6: Final answer
   x = 1,665.49