Finding the Fourth Proportional to 2,280.78, 3,139.74 and 1,690.20

Step by Step Solution

1. Step 1: Write the proportion equation
   2,280.78 : 3,139.74 = 1,690.20 : x
2. Step 2: Convert to fraction form
   2,280.78/3,139.74 = 1,690.20/x
3. Step 3: Cross multiply
   2,280.78x = 3,139.74 × 1,690.20
4. Step 4: Simplify right side
   2,280.78x = 5,306,788.55
5. Step 5: Solve for x
   x = 5,306,788.55/2,280.78
6. Step 6: Final answer
   x = 2,326.74