Finding the Fourth Proportional to 3,978.56, 5,489.76 and 2,486.72

Step by Step Solution

1. Step 1: Write the proportion equation
   3,978.56 : 5,489.76 = 2,486.72 : x
2. Step 2: Convert to fraction form
   3,978.56/5,489.76 = 2,486.72/x
3. Step 3: Cross multiply
   3,978.56x = 5,489.76 × 2,486.72
4. Step 4: Simplify right side
   3,978.56x = 13,651,495.99
5. Step 5: Solve for x
   x = 13,651,495.99/3,978.56
6. Step 6: Final answer
   x = 3,431.27