Finding the Fourth Proportional to 2,478.78, 3,420.47 and 1,431.18

Step by Step Solution

1. Step 1: Write the proportion equation
   2,478.78 : 3,420.47 = 1,431.18 : x
2. Step 2: Convert to fraction form
   2,478.78/3,420.47 = 1,431.18/x
3. Step 3: Cross multiply
   2,478.78x = 3,420.47 × 1,431.18
4. Step 4: Simplify right side
   2,478.78x = 4,895,308.25
5. Step 5: Solve for x
   x = 4,895,308.25/2,478.78
6. Step 6: Final answer
   x = 1,974.89