Finding the Fourth Proportional to 2,621.12, 3,930.16 and 1,389.12

Step by Step Solution

1. Step 1: Write the proportion equation
   2,621.12 : 3,930.16 = 1,389.12 : x
2. Step 2: Convert to fraction form
   2,621.12/3,930.16 = 1,389.12/x
3. Step 3: Cross multiply
   2,621.12x = 3,930.16 × 1,389.12
4. Step 4: Simplify right side
   2,621.12x = 5,459,463.86
5. Step 5: Solve for x
   x = 5,459,463.86/2,621.12
6. Step 6: Final answer
   x = 2,082.87