Finding the Fourth Proportional to 2,688.72, 4,033.41 and 840.30

Step by Step Solution

1. Step 1: Write the proportion equation
   2,688.72 : 4,033.41 = 840.30 : x
2. Step 2: Convert to fraction form
   2,688.72/4,033.41 = 840.30/x
3. Step 3: Cross multiply
   2,688.72x = 4,033.41 × 840.30
4. Step 4: Simplify right side
   2,688.72x = 3,389,274.42
5. Step 5: Solve for x
   x = 3,389,274.42/2,688.72
6. Step 6: Final answer
   x = 1,260.55