Finding the Fourth Proportional to 2,505.21, 3,456.78 and 1,386.20

Step by Step Solution

1. Step 1: Write the proportion equation
   2,505.21 : 3,456.78 = 1,386.20 : x
2. Step 2: Convert to fraction form
   2,505.21/3,456.78 = 1,386.20/x
3. Step 3: Cross multiply
   2,505.21x = 3,456.78 × 1,386.20
4. Step 4: Simplify right side
   2,505.21x = 4,791,771.15
5. Step 5: Solve for x
   x = 4,791,771.15/2,505.21
6. Step 6: Final answer
   x = 1,912.72