Finding the Fourth Proportional to 2,255.78, 3,112.90 and 1,261.05

Step by Step Solution

1. Step 1: Write the proportion equation
   2,255.78 : 3,112.90 = 1,261.05 : x
2. Step 2: Convert to fraction form
   2,255.78/3,112.90 = 1,261.05/x
3. Step 3: Cross multiply
   2,255.78x = 3,112.90 × 1,261.05
4. Step 4: Simplify right side
   2,255.78x = 3,925,522.55
5. Step 5: Solve for x
   x = 3,925,522.55/2,255.78
6. Step 6: Final answer
   x = 1,740.21